Epithelial cyst of the spleen.

This is a report of a case of epithelial cyst of the spleen in an 8-year-old boy. The cyst showed squamous metaplasia on histology. The risk of malignant transformation is discussed.

INTRODUCTION

Splenic cysts may be parasitic or non-parasitic in origin. Primary cysts are also called true, congenital, epidermoid or epithelial cysts. The treatment has changed drastically from total splenectomy in the past to splenic preservation methods now. Malignant transformation has been reported in a few cases in the literature.

CASE REPORT

An 8-year-old boy was admitted with pain in the left upper abdomen for 6 months. The pain was dull aching and he had low-grade fever off and on. There was no history of trauma, significant medical illness or surgical intervention in the past. He was pale and the abdominal examination revealed mild tenderness in the left hypochondriac region and splenomegaly. His hemoglobin was 10.5 g%. Other blood investigations were normal.

An ultrasonography of the abdomen was suggestive of a well-defined, encapsulated, mixed echogenic lesion in the posterosuperior surface of the spleen of 250-300 cc in volume. Contrast-enhanced computed tomogram (CECT) of the abdomen showed a space-occupying lesion of the spleen. He had undergone percutaneous aspiration of the cyst, which revealed 250 ml of greenish-colored fluid with no growth of microorganisms. Polyvalent pneumococcal vaccine was administered.

At laparotomy, the spleen was enlarged and densely adherent to the stomach on its anterior and medial sides. There were adhesions with the pancreas and also dense, inseperable adhesions with the diaphragm. There was a cystic area with surface discoloration on the posterosuperior surface of spleen. Intraoperative aspiration of the cystic area resulted in 200 ml of greenish-colored fluid. Total splenectomy was performed in view of the dense adhesions to the adjacent structures, large size of the cyst even after aspiration and the inability to leave behind adequate viable splenic parenchyma after cyst dissection [Figure 1]. Pus culture did not show any growth of organisms. The histopathology report of the specimen of spleen showed cysts lined by cuboidal epithelium in continuation with a stratified squamous lining, suggestive of metaplasia [Figure 2]. The diagnosis on histopathology was epithelial (primary) splenic cyst.

Figure 1

Specimen after opening the cyst

Figure 2

Squamous metaplasia in the cyst

The post-operative course was uneventful and he was asymptomatic at the 3 months follow-up.

DISCUSSION

Splenic cysts are very rare. Fowler and Martin classified splenic cysts based on the presence or absence of cellular lining of the cystic wall as primary (true) or secondary (pseudo) cysts.[12] Most true splenic cysts are epithelial in origin and have embryonic inclusion of epithelial cells from adjacent structures.[3] Splenic cysts may be of parasitic or non-parasitic origin. Congenital splenic cysts are also called epidermoid or epithelial cysts. They are uncommon, comprising only about 10% of all splenic cysts and 25% of non-parasitic cysts. Congenital splenic cysts form when there is an invagination of the mesothelium-lined splenic capsule during development. The lining is pluripotential and may undergo metaplastic changes and fluid accumulation with resultant cyst expansion. Cysts are asymptomatic, or they present with vague abdominal pain, abdominal mass or they are incidental findings during abdominal ultrasonography.

Splenic epithelial cysts occur predominantly in the second and third decades of life but can occur in children and even in infants.[4] Small cysts are usually asymptomatic. An asymptomatic painless abdominal mass is the presenting feature in 30-45% of the cases. Splenic cysts may present with localized or referred pain relating to splenomegaly, abdominal distension and mass effect. The initial symptoms are primarily gastrointestinal and include vague abdominal pain, early satiety, nausea, vomiting and dysphagia.[5]

Histologically, epidermoid cysts have a squamous epithelial lining with intracellular bridges and a thick collagenous wall. The interior cyst wall may be composed of thick trabeculated fibrous bands covered by epithelium. The cystic fluid may contain cholesterol crystals, protein particles or breakdown products of hemorrhage. The cellular lining of congenital cysts is thought to arise from infolding of the peritoneal mesothelium following splenic capsule rupture or from mesothelial cells trapped in the splenic sulci. The mesothelium undergoes metaplasia to squamous epithelium secondary to chronic irritation. Another postulation is that congenital cysts arise from the normal lymph spaces in the spleen.[6]

A comprehensive differential diagnosis for a cystic lesion of the spleen includes parasitic ecchinococcal disease, congenital cyst, intrasplenic pancreatic pseudocyst, pseudocysts from splenic trauma, infarction, infection, pyogenic splenic abscess, metastatic disease and cystic lymphangioma/hemangioma (rare).

The physical examination is usually normal, aside from an occasional abdominal mass. Routine laboratory studies are also normal. Tumor markers, carcinoembryonic antigen (CEA) and CA19-9, may be elevated and hence checked.[7] A direct relationship exists between these tumor marker elevation and splenic cysts. There is intense immunoreactivity of the inner lining of the cyst to anti-CA 19-9 antibodies.[8] Serum levels of the markers may lag behind actual elevations within the cystic cavity. The pre-operative and post-operative levels documenting a change to differentiate benign from malignant process is essential.

Ultrasonography shows that the cysts are either anechoic or hypoechoic.[910] Splenic cysts have historically been treated by splenectomy. Currently, the trend has shifted to more conservative surgery with the demonstration of increased mortality of splenectomized patients due to overwhelming post-splenectomy sepsis. Because of the increased risk of complications, splenic cysts with a diameter larger than 4-5 cm should be managed surgically[11] because conservative options, such as percutaneous aspiration or sclerosis, do not result in long-term control. There are different types of surgical treatment according to the patient's age and the size, location and nature of the cyst. The classical approach to splenic cysts has been open complete splenectomy.

Today, the options are percutaneous aspiration or percutaneous drainage, partial splenectomy with a stapler or harmonic scalpel, total cystectomy, marsupialization or cyst decapsulation (unroofing), laparoscopic puncture and creation of a cyst peritoneal window. Access can be either by open laparotomy or laparoscopy. Partial splenectomy preserves more than 25% of the splenic parenchyma, which is the minimal splenic tissue to preserve immunologic protection without increasing the risk of recurrence.[12]

In our case, as a result of previous aspiration and percutaneous drainage that the patient underwent before admission to the hospital, dense inflammatory adhesions around the spleen occurred making any possibility of splenic preservation surgery highly unlikely. Another technique to avoid splenectomy in this case was partial splenic decapsulation (marsupialization), which involved a trocar decompression of the cyst with removal of the outer splenic capsule, a running locking suture in the splenic wall and external drainage. However, the possibility of a malignancy developing in the splenic remnant prompted us to opt for a complete splenectomy.

Any type of conservative procedure is difficult to perform if the cyst is very large, is located in the splenic hilum or is covered completely by the splenic parenchyma (intrasplenic cyst), dense vascular adhesions to adjacent structures or if there are multiple cysts (polycystic cases); in these cases, a complete splenectomy should be performed either using the open or the laparoscopic approach.