Diagnosis and treatment of pancreatic pseudocysts and cystic tumors based on own material and quoted literature.

Pseudocysts constitute the most basic cystic lesions of the pancreas. Symptomatic cysts may be treated by means of both minimally invasive methods and surgery. Currently, it is believed that approximately 5% of cystic lesions in the pancreas may in fact, be neoplastic cystic tumors. Their presence is manifested by generally irregular multilocular structures, solid nodules inside the cyst or in the pancreatic duct, frequently vascularized, as well as fragmentary thickening of the cystic wall or septation. AIM: The aim of this paper was to present current management, both diagnostic and therapeutic, in patients with pancreatic pseudocysts and cystic tumors. The article has been written based on the material collected and prepared in the author's Department as well as on the basis of current reports found in the quoted literature. MATERIAL AND METHODS
RESULTS: In 2000-2012, the Second Department of General, Gastrointestinal and Oncological Surgery of the Alimentary Tract treated 179 patients with cystic lesions in the region of the pancreas. This group comprised 12 cases of cystic tumors and 167 pseudocysts. Twenty-three patients (13.8%) were monitored only and 144 received procedural treatment. Out of the latter group, 75 patients underwent drainage procedures and 48 were qualified to endoscopic cystogastrostomy or cystoduodenostomy. The endoscopic procedure was unsuccessful in 11 cases (23%). In a group of patients with a pancreatic cystic tumor (12 patients), 6 of them (50%) underwent therapeutic resection of the tumor with adequate fragment of the gland.
CONCLUSIONS: Endoscopic drainage is an effective and safe method of minimally invasive treatment of pancreatic cysts. The patients who do not qualify to endoscopic procedures require surgical treatment. The differentiation of a neoplasm from a typical cyst is of fundamental significance for the selection of the treatment method.

The advancement of diagnostic imaging has indisputably contributed to more frequent detection of cystic lesions in the region of the pancreas. The most common are nonneoplastic pseudocysts which are associated with complicated cases of acute or chronic pancreatitis and with posttraumatic or postoperative changes(. Cystic lesions of the pancreas include a very important group, namely, pancreatic cystic tumors. Mistaking a neoplastic cyst for a pseudocyst may have serious implications and may delay the commencement of an adequate therapy(.

The incidence of pseudocysts in the population is estimated at 0.5–1.0 in 100 000 adults per year(. They include retention and post-necrotic cysts which have a circumscribed capsule. Retention cysts form as a result of an existing obstacle in the pancreatic ducts which is localized on their various levels and inhibits juice outflow (fig. 1). This may be caused by a neoplastic or inflammatory tumor, ductal stones, ductal narrowing or a different type of obturation(. Post-necrotic cysts are associated with acute pancreatitis (AP) and develop following local damage to the gland with the formation of fistulae. A cistern, which mainly contains irritative pancreatic juice, is the cause of an inflammatory reaction of adjacent tissues and creation of the capsule that surrounds it. A post-necrotic cyst may contain fragments of pancreatic or adipose tissue sequesters (fig. 2)(. A serious complication which forces early therapeutic intervention is bacterial infection of the contents of the cyst, which, if appropriate treatment is not implemented, may result in spreading of the inflammatory process to the surrounding tissues(.

Fig. 1

Pancreatic retention pseudocyst in association with chronic pancreatitis. Parenchymal calcifications (arrow), ductal dilatation (Wirsung) and atrophy of the parenchyma

Fig. 2

Post-necrotic pseudocyst that develops after an episode of acute pancreatitis. Such a pseudocyst is well-defined by a fibrous capsule, usually contains enzymatic fluid and necrotic debris (arrow)

Selecting a treatment method of a pancreatic pseudocyst may pose a considerable problem. Within the last dozen or so years, the development of minimally invasive techniques rendered their efficacy comparable to or even better than that of a classical surgical drainage(. Despite the fact that endoscopic drainage, laparoscopic techniques or interventional radiology are more and more widespread and popular, patients are still frequently qualified to classical drainage procedures. The ideal surgical treatment would be a complete removal of a cyst since there is a risk of its becoming malignant in the future. However, the possibilities to perform such a procedure in practice are quite limited(.

Endoscopic internal drainage is an alternative to surgical drainage(. The lumen of the cyst may be connected to the gastrointestinal tract by puncturing the gastric wall (cystogastrostomy), duodenum (cystoduodenostomy) or by placing a stent in the main pancreatic duct (transpapillary cystostomy). The procedure is guided by endoscopic ultrasound (EUS) and Doppler sonography(. This enables precise assessment of the puncture site and localization of the blood vessels, which increases the safety of the procedure and minimizes risks of adverse effects. The choice of the drainage type depends on the localization of the cyst in relation to the gastrointestinal structures, gastric wall, duodenum and lesions in the pancreatic duct. When a connection of the pancreatic duct to the lumen of the cyst is detected, transpapillary drainage constitutes a method of choice(.

Benign cysts do not require to be resected and drainage procedure is indicated when certain symptoms are present and when the lesion is large or enlarging within the observation period(. In the case of such management, it is vital to unambiguously differentiate benign cysts from neoplastic cystic tumors of the pancreas(. Neoplastic cysts are usually related to a completely different clinical history with no acute episodes. The etiology of cystic tumors is not associated with a prior history of pancreatitis and it is neither related to alcohol consumption nor to cholelithiasis(. Despite considerable advancement in the field of diagnostic techniques, which has taken place in the recent years, differential diagnosis and related therapeutic management still seem to be controversial(. In the majority of centers, when no malignant transformation is observed in asymptomatic patients, only monitoring is recommended. Surgical resection is performed in patients with a high probability of malignant transformation(.

Imaging diagnosis is currently the main factor in differential diagnosis of pancreatic cystic lesions. The basic imaging examinations include: transabdominal ultrasound (US) and computed tomography (CT)(. Such tests help to detect a circumscribed fluid area in the region of the pancreas as well as estimate the thickness of its walls and evaluate its contents. Tracing the manner in which the cyst adheres to the gastrointestinal structures, vessels located in the vicinity of the pancreas and main visceral vessels is also significant since it is decisive when resection is considered(. Another test, which is currently more and more frequently recommended, is endoscopic ultrasound examination. It is significant both in diagnosing cystic lesions and neoplastic tumors as well as in supervising minimally invasive diagnostic and therapeutic procedures(.

Abdominal US and CT examinations are frequently insufficient to unambiguously differentiate between complicated cysts of the pancreas or suspicions of a neoplastic lesion. Neither are they sufficient for the selection of the type of interventional treatment. Therefore, in certain cases, additional examinations are performed, such as: contrast-enhanced ultrasound (CEUS), endoscopic retrograde cholangiopancreatography (ERCP), magnetic resonance imaging (MRI), magnetic resonance cholangiopancreatography (MRCP), 18-fluorodeoxyglucose positron emission tomography (18-FDG PET), angiography, EUS, also with Doppler mode, intraductal endoscopy and sonography(.

Most cystic tumors of the pancreas are relatively small, asymptomatic and incidental findings(. Generally, they are detected in older persons usually during abdominal US or CT examinations carried out for various reasons(. It is estimated that US examination detects 0.2% of lesions. In the case of CT or MRI, the percentage is 0.7%(. Out of pancreatic cystic tumors, serous neoplasms are diagnosed mainly in women (65%) aged 62 (range: 35–84 years) and account for 32–39% of all diagnosed cystic tumors(. Similarly, mucinous tumors are usually encountered in women (95%) in mean age of 53 (range: 19–82 years) and account for 10–45% of pancreatic cystic tumors. Other lesions are: intraductal papillary mucinous neoplasm (IPMN), which accounts for 21–33% of cystic tumors and is usually detected at the age of 65, and the most rarely encountered – solid pseudopapillary neoplasm (SPN), which so far, has been detected in 600 patients – it develops mainly in women in their 30s or 40s(. Other rarely encountered lesions (< 1% of tumors) are: cystic non-functional islet tumors (NFITs), acinic cell cystadenocarcinomas, cystadenoma, cavernous angioma and lymphangioma, ganglioma as well as primary solid neoplasms which undergo cystic degeneration(.

Aim of the paper

The aim of this paper was to present current management, both diagnostic and therapeutic, of patients with pancreatic pseudocysts and cystic tumors. The article has been written based on the material collected and prepared in the author's Department taking into consideration contemporary approaches and opinions included in the references.

Material and methods

In 2000–2012, the Second Department of General, Gastrointestinal and Oncological Surgery of the Alimentary Tract treated 179 patients with cystic lesions in the region of the pancreas. The diagnostic procedures included: abdominal ultrasound and Doppler examinations, CT and in certain cases, also EUS and intraoperative ultrasound (IOUS). When a cystic tumor was suspected, contrast enhanced CT, MRI or MRCP were conducted. Patients with suspected or confirmed neoplastic tumors were included in a separate group of cystic lesions. The initial examination was transcutaneous ultrasound examination. The localizations of the tumors were diverse. The majority of the lesions adhered to the pancreas but their outer outlines could border on various parts of the gastrointestinal tract and the mesentery or could be localized in the extraperitoneal space. The exact specification of adherence to, e.g. head, body or tail of the pancreas, is quite troublesome. Therefore, in our Department, the description usually specifies to which aspect of the pancreas, proximal or distal, the cyst adheres. In the material presented herein, the proximal localization (head, body) was found in 118 cases and distal (body, tail) – in 61 cases. The remaining patients presented with multiple lesions with no direct connection to the pancreas. Most of the treated lesions ranged from 3 to over 25 cm.

In 2000, we introduced endoscopic treatment method of pseudocysts. If in transabdominal ultrasound examination, cysts with defined walls are detected, located near the stomach or duodenum and indenting their lumina, EUS and videoendoscopy are conducted to determine the indications for endoscopic cystogastrostomy or cystoduodenostomy. When the adequate puncture site in a non-vascular region has been selected in EUS, it is marked with dye, spot coagulation or, currently, an appropriate drainage set is placed, directly guided by EUS. With the use of the lateral-viewing duodenoscope and diathermy, the gastric wall and adjacent cyst are punctured. Subsequently, having conducted the aspiration attempt, the prosthesis is inserted which allows for free outflow of cystic contents (fig. 3 A–C). The efficacy of the procedure is evaluated in sonography. Up to 2012, a total of 48 patients were qualified to endoscopic drainage procedures.

Fig. 3 A

EUS. EUS-guided pancreatic pseudocyst drainage. Puncturing the pseudocyst and inserting a guidewire

EUS-guided cystogastrostomy. Insertion of the stent to the lumen of the pseudocyst

Effective endoscopic pseudocyst drainage. The pancreatic juice flows through cystogastrostomy (prosthesis is inserted to the lumen of the pseudocyst)

When the initial diagnosis cannot rule out a cystic neoplasm of the pancreas, the patient undergoes detailed imaging examinations, biochemical and serological tests as well as, in certain cases, fine-needle aspiration biopsy (FNAB).

Results

In the subject group of 179 patients with cystic lesions in the region of the pancreas, 12 presented with cystic tumors and 167 – with pseudocysts, both acute and chronic. From among all 167 cases with symptomatic cysts, 23 patients (13.8%) were monitored only (involution of the lesions during the observation period) and the remaining 144 patients were qualified to procedures.

In 75 patients (44.9%), surgical procedures were conducted. The resection of the cyst was possible in merely 4 cases, the remaining patients underwent drainage procedures. In 24 cases, cystogastrostomy (Jurasz procedure) was conducted and in 39 cases, Roux-en-Y cystojejunostomy was performed. In the remaining patients, complex procedures took place, such as drainage of several cysts or total drainage of pseudocysts and pancreatic duct, also performed according to Roux-en-Y technique. During postoperative monitoring period, complications were observed in 16% of patients.

Furthermore, 21 patients (12.6%) with thin-walled retention cysts secondary to acute pancreatitis (AP), were treated by external US-guided drainage. In 8 cases (38%), relapse or persistent pancreatic fistula were observed. These patients required surgical treatment.

In the period from 2000 to 2012, 48 patients (28.7%) were qualified to endoscopic cystogastrostomy or cystoduodenostomy if transabdominal ultrasound and subsequently, EUS had confirmed such qualification. In all cases, it was attempted to introduce an appropriate stent (prosthesis) to the cysts through the wall of the gastrointestinal tract. The efficacy of the procedure was usually evaluated on the second day following the procedure by means of US examination. Drainage was successful in 37 patients, 12 of whom required correction of drain placement and a repeated procedure was necessary. Due to technical reasons, the placement of the drain was impossible in 11 patients (23%) – they underwent surgical drainage instead.

During examination, 12 patients were diagnosed with pancreatic cystic tumors. All patients underwent imaging examinations, such as: US examination with Doppler mode, CT and in 4 patients, MRI and MRCP. FNAB with aspiration was performed in 6 patients. The analysis of the contents (cytology, level of markers, test for mucous content) was positive in only 2 patients. In the remaining cases the analysis was not reliable. Due to the results of imaging examinations, in 5 patients with slight lesions (mainly from 2 to 3 cm) in whom a benign serous cystic neoplasm was suspected (based on US/CT), observation was recommended. In this group, only one patient underwent FNAB (unreliable attempt). Evident growth of the tumorous lesion was not observed in the monitored patients within the observation period of 2–3 years. Thus, there were no indications for surgical treatment. In further 6 patients with over 4 cm lesions that showed features of neoplastic cystic tumors, resection of the tumor with an adequate part of the pancreas was performed. In 5 patients, FNAB was conducted (the result was positive only in 2 cases, see above). In 1 patient, a malignant neoplasm was confirmed which infiltrated adjacent structures and gave metastases to the liver. This case was considered inoperative (as assessed in diagnostic laparoscopy with tissue sample collection).

Discussion

In patients diagnosed with and treated due to pancreatic pseudocysts, transabdominal ultrasound is the main diagnostic tool, followed by CT and EUS, in qualifying patients to endoscopic treatment. In US examination, the thickness of the cystic wall must be determined. Thin-walled cisterns do not qualify to surgical treatment (anastomosis) due to the difficulties to perform anastomosis and the possibility of secondary leak. In such cases, external percutaneous drainage should be considered or, in certain favorable conditions – internal endoscopic drainage(. The treatment of pancreatic cysts should depend on their origin, character, size, location and individual clinical symptoms. It is statistically estimated that no more than 25% of cysts disappear spontaneously. Slight cysts – measuring not more than 4 cm – which appeared after acute pancreatitis receive conservative treatment(. They are usually necrotic collections of aseptic contents which do not contain any large breakdown fragments. Slight lesions, from 3 to 4 cm, which may be effectively controlled by means of periodical US examinations, do not receive any treatment provided that their neoplastic character has been ruled out(. Only large cysts are qualified to procedures – usually those measuring more than 5–6 cm – particularly when other characteristic clinical symptoms are present, such as pain, obstructive jaundice, obstruction in the upper gastrointestinal tract, decreased appetite or weight loss (fig. 2). A similar situation refers to cysts whose continuous growth is observed in US check-up examinations and complicated cysts. In accordance with current principles, uncomplicated cysts and fluid collections secondary to AP are not subject to treatment if the period of US observation and monitoring is shorter than 6 weeks(.

In the discussed period of time, from among 167 patients diagnosed with symptomatic cysts of the pancreas, 13.8% were treated conservatively, 44.9% underwent surgeries, 12.6% were treated by means of external drainage and 28.7% – by internal EUS-guided endoscopic drainage. Still, the largest group underwent surgeries in spite of the fact that endoscopic procedures introduced in 2000 have a greater and greater therapeutic value. Such a procedure was performed in 48 patients, but in 11 of them (23%) endoscopic drainage was not successful mainly due to technical problems connected with prosthesis placement, difficult angular access of the endoscope to the cyst, bleeding and suspicion of perforation. In such cases, surgical drainage is the method of choice(. In the remaining 37 patients with pancreatic pseudocysts, endoscopic drainage constituted a final procedure. Such a treatment is currently commonly recommended by the majority of centers. It allows for a rapid return to everyday activities, patients do not need to follow a rigorous diet (as it happens after a surgery) and their physical activity is not restricted due to the postoperative wound(.

At present, thanks to the advancement of diagnostic techniques, we may accurately assess and distinguish neoplastic cystic tumors of the pancreas from ordinary cystic lesions. It is currently believed that even 10% of all cases of cystic lesions are related to a neoplasm and that these lesions account for 1–5% of all pancreatic neoplasms(.

It is believed that asymptomatic lesions constitute approximately 35–75% of cystic tumors of the pancreas(. The appearance of certain symptoms may be associated with growth of the tumor, increased internal pressure or malignant transformation(. The most common reported symptoms include: pain in the abdomen, nausea, vomiting and increased circumference of the abdomen, weight loss, obstructive jaundice, constipation or diarrhea and weakness(. Patients with IPMN may be sometimes treated due to recurrent episodes of acute pancreatitis, particularly, in cases when the main pancreatic duct is involved(. Large tumors are most frequently found in patients with mucinous cystic neoplasms (MCN) and SPN – these lesions usually give symptoms of a midabdominal tumor(. Exacerbation of pain is associated with sudden hemorrhage to the tumor or results from its rupture (SPN). In advanced malignant lesions, apart from the above-listed symptoms the following may occur: bleeding from the gastrointestinal tract in the case of gastric infiltration, portal hypertension and hemobilia as well as, eventually, diabetes when the pancreas is considerably damaged(.

In the analyzed time period, 12 patients were diagnosed with cystic tumors of the pancreas. After thorough imaging analysis, including Doppler ultrasound, contrast enhanced CT as well as in some cases, MRI, MRCP and EUS, 6 patients were qualified to FNAB. Only in 2 cases did FNAB and assessment of the aspirated fluid confirm the presence of a cystic neoplasm. Similarly in the quoted references – imaging examinations are decisive when treatment-related decisions are made. The assessment of the aspirate is usually less specific and the final verification of the type of the tumor is acquired following the analysis of the postoperative specimen(. In our material, 6 patients were qualified to resection procedures. They presented with symptomatic, large (> 4 cm) cystic tumors. The postoperative verification confirmed the presence of 3 serous cystadenomas and 3 mucinous cystadenomas – in 2 cases, the lesions had already been identified as cystadenocarcinomas. In one patient, a malignant SPN tumor was detected with slight metastases to the liver – inoperative lesion. In further 5 patients, slight (2–3 cm) tumor-like lesions were visualized. They were identified as serous tumors which do not require surgical treatment. In these patients, annual check-ups were recommended which in the period of analysis, did not show any growth or change of the inner structure. According to numerous authors, such lesions do not require immediate qualification to resection and in the majority of cases, they do not change their appearance during the monitoring period(.

In the next part, the authors discuss the most frequent pancreatic cystic tumors. The material has been collected based on quoted recent publications concerning diagnosis, methods of differentiation and proposed types of treatment. The paper includes photographs acquired from the authors’ own clinical material.

Serous cystadenoma

Cystic tumors are relatively rare lesions and should be differentiated particularly with pancreatic cysts. Pancreatic serous neoplasms are generally benign with little malignancy potential(. They are usually solitary, with the size of 1.5–35 cm and constitute approximately 30% of all primary pancreatic cystic tumors(. We mainly encounter two types of such lesions: microcystic cystadenomas and macrocystic or oligocystic cystadenomas. The microcystic form usually develops in women at the age of 50–60 and its typical localization is the body and tail of the pancreas(. It is usually asymptomatic and signals, such as pain in the abdomen, weight loss, feeling of distension in the epigastric region and peristalsis disorders appear when the lesion shows large growth(. A typical form of the tumor is composed of a large number of small cysts lined with cuboidal epithelium producing glycogen. The size of the cysts ranges from 0.2 to 2.0 cm and the entire tumor measures 1.4–30 cm(. The lesion may grow locally leading to almost complete damage of the healthy pancreatic tissue(. In imaging examinations (US, CT), such a cystic tumor frequently has the appearance of a “honeycomb” which is related to a large number of small cysts (fig. 4 A, B). The lesion is relatively well-circumscribed with a central scar or, sometimes, with a calcification. It may also contain a large number of fibrous septations (fig. 4 C, D). The cysts are filled with watery, sometimes sanguineous fluid without any mucous contents(.

Fig. 4 A

Serous cystadenoma (microcystic type). A typical serous tumor is composed of multiple small cysts and has a “honeycomb” appearance. The cystic mass is situated in the pancreatic tail, about 5 cm in diameter

Fig. 4 B

IOUS. Well-defined microcystic tumor, poorly vascularized, adhering to the splenic vessels (arrow) (color Doppler)

Fig. 4 C

Doppler US. Serous cystadenoma in the head of the pancreas, poorly vascularized, 5.6 cm in diameter. Similar “honeycomb” structure with oligocystic components and central scar (arrow)

Fig. 4 D

Contrast-enhanced CT shows a classic serous cystadenoma in the head of the pancreas (4.1 × 2.9 cm). The lesion has the appearance of a solid mass with numerous small cysts and septations – “honeycomb” structure. The calcified central scar (arrow)

The other form of the tumor, i.e. macrocystic or oligocystic cystadenoma, with its appearance resembles a mucinous cystic tumor and is difficult to differentiate based on imaging examinations. It develops equally frequently in men and women, usually, after the age of 40. The lesion is mainly localized in the head of the pancreas. Therefore, the basic symptoms of its presence, next to the feeling of discomfort in the epigastric region and sometimes, pain when the lesion grows, is jaundice – it is not, however, a dominant symptom(. The tumor is composed of other well-circumscribed cystic lesions, with their diameters usually greater than 2 cm. They are generally single cysts or there are a few poorly circumscribed ones with some internal septations(.

In the present-day imaging diagnosis, CEUS is gaining recognition. It is a modern US examination with the use of contrast media which considerably broadens diagnostic possibilities of Doppler US examination. CEUS allows for a good visualization of the “honeycomb” appearance and of the septations inside a neoplastic cyst(. When, in small cystic tumors, which do not qualify to surgical treatment, CEUS is performed, there is no need for further examinations, such as MRI, MRCP and even contrast enhanced CT(.

Another recommended examination is EUS. Owing to the high resolution, one may visualize lesions composed of very slight cysts (of 5 mm in diameter) in a more detailed manner as compared to conventional ultrasound. Moreover, EUS examination enables precise visualization of the “honeycomb” structure, calcifications and internal septations(. It appears that a confirmation of a microcystic structure is sufficient for differential diagnosis and there is no need for the analysis of the fluid collected by means of EUS-guided fine-needle aspiration biopsy (EUS-FNA) (. What is more, the collection of adequate amount of fluid from such slight structures is frequently not feasible. These guidelines were followed in the cases diagnosed in our Department. Fluid aspiration and its examination seem necessary when a larger cyst with a suspected neoplastic character has been visualized(. This is of considerable significance in differentiation with mucinous cystic tumors(. In serous tumors, the collected fluid does not show any traces of mucin or amylase, and the test for the contents of cell elements (cytological examination) is possible in less than 50% of cases. Contrary to patients with marked malignant transformation, the level of tumor markers (mainly CEA) is low, usually below 5 ng/ml(. In the material presented herein, in the case of serous tumors, aspiration demonstrated correct level of the markers (CEA and CA 19-9) and cytological examination did not reveal any neoplastic cells.

A great majority of pancreatic serous tumors are benign – the possibility of their malignant transformation concerns less than 3% of cases(. A surgical resection of such a tumor together with a fragment of the pancreas is indicated in symptomatic lesions, in tumors that grow during the period of monitoring and in cases in which malignant transformation cannot be ruled out(. In patients qualified to surgical treatment, IOUS appears to be useful both in terms of final verification of the diagnosis and in the assessment of the range of resection(. According to the quoted literature, the size of the tumor at which surgery should be considered is over 4–5 cm( (fig. 5 A–C). Up to 4 cm, tumors tend to grow slowly (on average, 0.12 cm/year). The biology of tumors changes with their size. It was observed that tumors larger than 4 cm grow faster (on average, 1.6 cm/year), symptoms begin to appear and malignant transformation becomes more possible(. Unambiguous preoperative confirmation of such a transformation is rarely possible. It may happen that in imaging scans, a tumorous lesion shows local infiltration on its surrounding structures but the possibility to diagnose carcinoma based on imaging methods, endoscopic techniques and biopsy are limited. Only surgical resection can verify the diagnosis(.

Fig. 5 A

Computed tomography. Serous cystadenoma situated in the pancreatic body. A symptomatic lesion, 5.5 cm in the diameter, qualified to surgical resection

IOUS. Micro- and oligocystic serous cystadenoma, “honeycomb” appearance. During surgical resection

Serous cystadenoma, after surgical distal resection of the pancreas. Postoperative specimen

The debate whether serous tumors should be only observed or at once qualified to surgical treatment is still open. There are mixed opinions since the cost of check-ups is considerable and the sole awareness of patients of a potential threat to develop a cancerous disease is of great significance. Thus, slight lesions with 2–3 cm in diameter should be observed (fig. 6). Check-up examinations, including US and CT, ought to be performed at least every 1–2 years. In the remaining cases, resection of the tumor should be considered. It might be performed with the application of minimally invasive techniques when the lesion is relatively small and when surgical treatment should proceed with no complications(. In our Department, the aforementioned principles are observed.

Fig. 6

Contrast-enhanced CT – a small hypodense cystic tumor in the pancreatic tail (2.5 × 2 cm). Poorly vascularized, multiple small cysts with polycyclic border of the tumor

Mucinous cystadenoma (cystadenocarcinoma)

It is currently believed that mucinous cystic tumors constitute the most common form of pancreatic cystic neoplasms (10–45%)(. Due to the fact that in numerous cases they resemble ordinary cysts, a proper differentiation between these two is essential. They are encountered almost only in women (95%), mainly middle-aged ones, and are usually localized in the body and tail of the pancreas(. A mean size of the tumor during the first diagnosis equals > 5 cm and in certain cases, the lesion may grow even up to 25–35 cm(. Such lesions are usually solitary and do not maintain any connection with the main pancreatic duct(.

The most frequently encountered form of such a tumor is a single large lesion of cystic character with or without internal septations and with a well-defined, usually thickened outer wall (fig. 7)(. The cyst is lined with columnar epithelium which produces mucus that forms its inner layer. The outer layer is made up of stroma which resembles ovarian structure(. These cysts usually contain a certain amount of mucous substance and one may also find sanguineous contents after hemorrhages or necrotic changes. Typical radiological features of the tumor include: septations, solid intramural nodules and peripheral calcifications(. In ultrasound examination, a mucinous tumor is visualized as a hypoechoic, well-circumscribed mass with diverse, often irregular thickening of the wall and sometimes, with solid nodules or calcifications(. CEUS examination allows for a better identification of the lesions within the wall (nodules) and thickened septations, which is caused by increased vascularity of the altered structures attesting to malignant transformation of the tumor(. From the histological viewpoint, intramural nodules may represent high-grade dysplasia or forms of invasive carcinoma(. The visualization of the symptom triad, i.e. irregular cystic wall thickening, peripheral calcifications and intramural solid lesions, in US, CT or MRI may correspond to malignant transformation even in 95% cases( (fig. 8 A, B). Only a slight per cent of mucinous cystic tumors present a microcystic form, usually a slight one, single with few septations. In such cases, differential diagnosis is particularly difficult(.

Fig. 7

IOUS. Uni- or multilocular mucinous cystadenoma with septations composed mainly of large cystic lesions. Normal pancreatic tissue (T). The cystic lesion is situated in the head of the pancreas with low-grade dysplasia (arrows)

Fig. 8 A

US – power Doppler. Mucinous cystadenocarcinoma. Irregular cystic wall thickening, peripheral calcifications and intramural solid nodules – signs of malignancy. Tumor in the body/tail of the pancreas, 6.5 cm in diameter. Qualified to surgical resection

Fig. 8 B

IOUS. Mucinous cystadenocarcinoma during surgical resection, estimation of tissue infiltration. Cystic neoplasm with reduced fluid capacity, mainly growth of solid tissue

In order to learn the morphology of cystic tumors, EUS examination is performed. This imaging modality provides reliable information allowing for the characterization of the cyst and determining the possibilities of resection when features of malignancy are present(. Due to the extension of the method to include aspiration biopsy (EUS-FNA), it is possible to find extracellular mucus in the cystic fluid, conduct cytological or, more rarely, histological analyses, make biochemical assessment, determine the level of tumor markers and perform molecular analysis(. As for cytological analysis, the accuracy of the test in various samples equals 50%(. The reasons may be technical difficulties to collect fluid (too little amount) or low contents of cell elements in the aspirate. From among numerous tumor markers, the most specific is carcinoembryonic antigen – CEA. With the cut-off value of 200 ng/ml, higher values obtained in the analysis of cystic fluid indicate the presence of a mucinous tumor. In the statistical analysis for this level, the sensitivity constituted 62%, specificity – 93% and accuracy – 73%(. A similar situation may be observed in the analysis of amylase concentration in the fluid. For the cut-off value of 250 IU/L, lower values indicate that the lesion is not a pseudocyst but a cystic tumor. In the case of this level, the sensitivity and specificity constituted 45% and 89% respectively. Unfortunately, the papers published so far do not specify the level of CEA marker above which the cancerous transformation might be confirmed(. This is verified after thorough evaluation of all data, particularly, imaging examinations and possible findings of EUS-FNA.

What is important is the fact that small mucinous tumors may manifest no symptoms in as many as 75% of patients. When symptoms appear, the tumor is usually large and potentially malignant. Therefore, in all such cases rapid diagnosis and surgical resection of the tumor are essential(. The basis for the qualification to surgical treatment is the outcome of imaging examinations, clinical examination and, to a lower degree, also data obtained from cystic fluid aspiration(. When a mucinous tumor of the pancreas is identified, one should remember that such lesions are frequently malignant or of highgrade dysplasia and they qualify to surgical treatment. A total evaluation of the tumor's character is possible only following its resection, after histopathological examination(. In our material, the examination of a postoperative specimen verified the presence of malignant mucinous tumors in two patients. Aspiration biopsy performed prior to the procedure revealed elevated CEA level and presence of mucus. Cytological examination gave positive outcomes in the analysis of fluid from the inside of the cystic tumor in only one patient.

Intraductal papillary mucinous neoplasm (IPMN)

This type of tumor is usually encountered in elderly men, aged 60–80. In a large majority of patients, these lesions manifest no symptoms. The most common symptom is recurrent pain, similar to that in the course of chronic, exacerbating pancreatitis or episodes of acute pancreatitis, occurring mainly after meals(. The pain depends on increased mucus secretion by the tumor's cells. Such mucus travels to the pancreatic duct where it contributes to large pressure rise, which causes significant dilatation of the duct(. Other symptoms include: weight loss, jaundice, steatorrhea and diabetes(.

The features of the tumor's image depend on its type and localization in the pancreas. We distinguish three types of IPMN: central type which encompasses the main pancreatic duct, peripheral type involving the branches of the ducts, and mixed-type(. The central type is the most common (even up to 75% of cases). The lesion looks like a papilloma or polyp originating from the epithelium of the pancreatic duct. The changes are the effect of highgrade dysplasia of a borderline type or even a cancerous lesion (local or invasive)(.

The peripheral type, which is encountered much more rarely, is mainly localized in the region of the uncinate process. One of the features of its morphological presentation is a set of cysts resembling “a cluster of grapes.” The connection with the pancreatic duct is also characteristic(. The cystic appearance of the lesion renders it similar not only to a mucinous tumor, but also to a pseudocyst. The “grape-like” presentation is caused by the dilatation of numerous peripheral pancreatic ducts filled with mucus. Sometimes, but rarely, instead of the lesion described above, a single, considerably dilated peripheral duct is visualized which forms the structure of the cyst(.

At present, imaging examinations, such as ultrasound, but CT and MRI in particular, are capable of relatively accurate visualization of the dilatation of the pancreatic duct, secondary cystic lesions and connection between the duct and altered, dilated cystic structure(. The decisive examinations in the case of IPMN are: MRCP, EUS and ERCP. ERCP allows for the identification of the intraductal lesions and collection of the pancreatic juice in order to determine the content of mucin, obtain a cytological picture as well as determine the level of tumor markers in the aspirate(. This examination may simultaneously wash out and even temporarily decompress the duct from dense mucus. MRCP, on the other hand, is the method of choice in the diagnosis and assessment of IPMN progression(. It may prove more accurate in identification of the peripheral types as compared to ERCP. The function of imaging examinations is also to determine a potential infiltration of adjacent tissues, enlargement of the lymph nodes or confirmation of existing metastases.

EUS allows for visualizing the connection between the main pancreatic duct and dilated peripheral ducts. The examination is also performed to differentiate between hypoechoic mucus and internal growths of papillary or polypoid type. It accurately assesses the thickening of the ductal wall and in peripheral types – the thickening of the cystic wall and presence of intramural nodules which are normally signs of malignant transformation(. The risk of developing a malignancy rises with the increase in the diameter of the main pancreatic duct, in the case of visualizing a large amount of mucus crossing through the ampulla of Vater and when obstructive jaundice and/or diabetes are clinically confirmed(. EUS examination is extended by EUS-FNA thanks to which we may conduct cytological tests, determine the concentration of tumor markers and amylase and perform FNAB of enlarged peripancreatic lymph nodes(.

The risk of malignant transformation of a central-type IPMN involving the main pancreatic duct is estimated at 70%. In the case of the peripheral type, it is 25%(. Therefore, there are specific indications for a surgical resection of a central-type tumor, even for total pancreatectomy if the main duct is involved to a great extent. When the tumor is localized peripherally, the decision concerning surgical treatment should be made based on the general condition of the patient and on associated risks and benefits of such a procedure taking into account the presence of given symptoms. Furthermore, the progression of the local tumor (> 3 cm) and other patient's conditions should also be taken into consideration(. In many cases intraoperative ultrasound examination helps to decide about the range of surgery and resection margin. It is also useful in differentiating between pancreatic cysts and cystic tumors if following the previous examinations, both imaging scans and others, there are still certain diagnostic doubts(.

Solid pseudopapillary neoplasm (SPN)

SPN is a rare tumor. So far, over 600 cases have been reported which constitutes approximately 1% of all cystic neoplasms of the pancreas(. In over 90%, it develops in women in the 2nd and 3rd decades of life. Usually wellcircumscribed, the tumor is composed of solid part, cystic lesions, papillary structures, areas of necrosis and hemorrhagic components which are a result of numerous extravasations into the tumorous tissue(. The tumors may develop both in the head and in the tail of the pancreas. Patients report abdominal pain and feeling of distension, jaundice occurs rarely(. The tumor may grow to various sizes. It has been reported to grow to 1–35 cm but the average size is 6 cm(.

The recommended imaging examinations in the diagnosis of SPN are: US, CT and MRI. The scans reveal a well-encapsulated, heterogeneous tumor with areas of cystic degeneration and hemorrhagic components. Other examinations include tumor marker assessment, recommended markers are as follows: α1-antitrypsin, α1-antichymotrypsin, neuron-specific enolase (NSE) and vimentin(. SPN shows a relatively low malignancy potential and the risk is estimated at 15%(. In 10–15% of patients, the neoplasm metastasizes to the liver, infiltrates vascular structures and adjacent organs (fig. 9 A–C)(. Such a case was reported in our clinical material. A surgical resection of the tumor with adequate portion of the pancreas (proximal or distal resection) is the treatment of choice. It is also recommended to surgically remove metastases and to perform lymphadenectomy. Even in such cases, the prognosis is good and longterm survival depends on the specific biology of the SPN tumor(. The remaining cystic neoplasms are encountered rarely and thus, their separate description is not needed.

Fig. 9 A

Solid pseudopapillary neoplasm (SPN). A large symptomatic lesion, well-circumscribed, surrounded by a thick capsule. The tumor localized in the tail of the pancreas, approximately 10 cm in diameter. The content of the lesion is solid with signs of necrosis or hemorrhage which are responsible for the cystic capacity. The tumor with malignant potential

Malignant transformation of SPN. Small metastases in the liver (arrow)

SPN. Contrast-enhanced CT scans show a mixed solid and cystic mass in the pancreatic head (10 × 7.5 cm). Thick, well-circumscribed capsule, hyperdense areas due to hemorrhage, and areas of necrosis

Conclusions

The procedural treatment is applied in the case of large (> 4 cm), symptomatic cysts of the pancreas.

Endoscopic drainage constitutes an effective and safe method of minimally invasive treatment of pancreatic cysts and surgical procedures are an alternative when minimally invasive techniques are not possible.

The differentiation of a neoplasm from a typical cyst is of fundamental significance for the selection of an adequate treatment method.