Acinar Cell Carcinoma of the Uncinate Process of the Pancreas in a Child Managed Sans Whipple's Procedure-a Rare Case Scenario.

Acinar cell carcinoma (ACC) is a rare malignant tumor of the pancreas. A 10-year-old girl presented with a large tumor arising from the pancreatic head. Excision sans Whipple's procedure was performed. Histopathology revealed it as ACC. In the context of this case, this rare tumor is being reported to highlight that such tumors arising from the head of the pancreas can be managed successfully without always resorting to a Whipple's procedure. Copyright:

INTRODUCTION

Pancreatic neoplasms are rare in children and have a different histologic spectrum and prognosis than those in adults.[1] Acinar cell carcinoma (ACC) represents approximately 1%–2% exocrine pancreatic neoplasms occurring in adults, and usually, they present late in adulthood, with a peak incidence in the 60 s.[23] However, in children, ACC accounts for nearly 15% of pancreatic tumors. We describe herein a case of ACC arising from the head of the pancreas in a girl managed sans Whipple's procedure with a gratifying outcome. The case is being reported to discuss the salient features of ACC and highlight the adopted unconventional surgical approach.

CASE REPORT

A 10-year-old girl presented with a slow-growing abdominal lump of 3 years duration. There was no history of any associated symptoms. She had undergone a laparotomy and incisional biopsy of the mass in another hospital, along with a 6-month course of two-drug (alternating 4-weekly cycles of cisplatin and cyclophosphamide) chemotherapy 15 months before presenting to us.

On examination, the abdomen was distended, with a right supraumbilical transverse healed surgical scar. There was a mass measuring approximately 20 cm × 10 cm occupying the epigastric, umbilical and the right lumbar regions with a smooth surface, and was mobile horizontally. Radiologically, it was found to be a large solid heterogeneous mass (14 cm × 9.3 cm × 9 cm) arising from the pancreatic head. The mass had well-defined margins and was pushing the pancreas anteriorly, and had close contact with it [Figure 1a–c]. It was also pushing the small bowel inferiorly, and a diagnosis of pancreatic neuroendocrine tumor was made provisionally. Metastatic workup was negative. The incision biopsy was reviewed, and revealed a neoplasm with pancreatic acinar differentiation, with the possibilities of pancreatoblastoma and ACC being considered.

Figure 1

(a-c): Axial (A, B) and coronal reformatted (c) computed tomography images reveal a large enhancing heterogeneous mass (asterisk) in right upper quadrant of abdomen. Note the foci of calcification (arrows) and necrosis (arrowhead). The mass is in relation to the uncinate process of pancreas

A Whipple's procedure for excision was planned. Intraoperatively, a large (14 cm × 12 cm × 7 cm) encapsulated and exophytic mass arising from the pancreatic head was found. A closer examination confirmed that it was arising from the uncinate process with a distinct stalk. Excision of the mass along with the stalk with a cuff of the normal looking uncinate process was performed. Enlarged peripancreatic and mesenteric lymph nodes were also sampled and sent for histopathological examination (HPE).

The child had a smooth postoperative course. HPE of the resected tumor showed a cellular neoplasm with lobular architecture. Tumor cells had moderate to abundant granular eosinophilic cytoplasm which showed Periodic acid–Schiff–diastase (PAS-D) positivity, and basally placed uniform round vesicular nuclei with inconspicuous nucleoli. The cells were arranged predominantly in solid pattern; acinar, glandular, and trabecular patterns were rare. Squamous islands and fibrous bands were not identified despite extensive sampling. Foci of necrosis were present [Figure 2a-f].

Figure 2

Photomicrographs show a lobulated tumor (a; H and E, ×10) with foci of necrosis (b; H and E, ×10) and cells arranged in sheets (c; H and E, ×20), glandular (d; H and E, ×20) and acinar (e; H and E, ×20) patterns; tumor cells have abundant granular cytoplasm and vesicular nuclei (f; H and E, ×40), are positive for chymotrypsin (g; immunohistochemistry, ×20) and low Ki-67 labeling index (h; H and E, ×20)

On immunohistochemistry (IHC), the tumor cells were positive for cytokeratin, chymotrypsin, and chromogranin in occasional cells, while epithelial membrane antigen, synaptophysin, CD56, CD10, carcinoembryonic antigen, gastrin, glucagon, insulin, somatostatin, progesterone receptor, beta-catenin, and p53 were negative. Ki-67 labeling index was 3%–4% [Figure 2g and h)]. A final diagnosis of pancreatic ACC was made. The resection margin was free. After 3 years of follow-up, there are no clinical or radiological features of tumor recurrence.

DISCUSSION

Pancreatic neoplasms are divided into epithelial and nonepithelial types. Epithelial tumors may be further classified as exocrine or endocrine. Exocrine tumors may be of acinar, ductal, or undetermined cell origin.[1] Pediatric cases form only a small fraction (6%) of all ACCs and are commonly encountered at around 8–15 years of age.[4] Confirming the diagnosis of ACC preoperatively is difficult, as pancreatoblastoma is a close differential diagnosis.

ACC is a well-known entity but because of its rarity, a single institution is highly unlikely to treat many patients with ACC.[5] In a retrospective review of all patients <21 years of age with malignant pancreatic tumors at Memorial Sloan Kettering Cancer Center, it was noted that only one patient had ACC, with the pancreas itself cited as an organ harboring much lesser tumors in children overall.[6]

Males are affected more frequently than females, with a male-to-female ratio of 2–3:1. The presenting symptoms are most often nonspecific and related to local tumor growth or metastases, as in our case, having painless long standing abdominal lump. The most common complaint mentioned in the literature is abdominal pain.[1] Others include nausea, vomiting, obstructive jaundice, anorexia, and weight loss. Atypical presentations are common, like Cushing syndrome in a child reported by Illyés et al.[3]

Few reports describe the imaging appearance of this rare tumor. Sonographically, a well-defined, predominantly hypoechoic mass may be appreciated, whereas, in computed tomography scan, the tumor is almost always well-demarcated, frequently exophytic tumors with a heterogeneous internal architecture.[5] In our case, the radiological findings matched with the features as available in the literature.

Microscopically, ACCs are composed of cells showing acinar differentiation, arranged in acinar, solid, glandular, and trabecular patterns, which may coexist.[7] In children, the challenge lies in their differentiation from pancreatoblastoma as they are similar macroscopically and microscopically, owing to their common acinar differentiation. In addition, both ACC and pancreatoblastoma have a similar histochemical and IHC profile, with cytoplasmic PAS-D positive granules, and immunoreactivity with trypsin, chymotrypsin, lipase, and BCL10.[7] The distinguishing features of pancreatoblastoma are squamoid corpuscles and prominent stroma, which are absent in ACC.[1] Further, electron microscopy demonstrates zymogen, neuroendocrine, and mucin granules in pancreatoblastoma, but only zymogen granules in ACC; however, electron microscopy is not readily available and usually not performed for diagnosis. ACC can occasionally be confused with pancreatic neuroendocrine tumors due to the focal expression of chromogranin or synaptophysin in a significant proportion of cases (35%–54%).

In children, resections have been reported to be comparatively easier and better tolerated. Among the reported resected cases of ACC, it was generally solitary and large but grew by compressing against the surrounding tissue and was often covered by a fibrous capsule, with the tumor often arising in the pancreatic head.[5] A case quite similar to the one described in our report underwent a pylorus-preserving pancreatoduodenectomy (PPPD) with D1 lymphadenectomy and reconstruction by the modified Child's procedure and pancreatojejunostomy with complete drainage as the tumor was continuous with the head of the pancreas.[8] PPPD or modified Whipple's procedure has been described as the first choice for the patient without distant metastasis, which was also planned for this case but later on tailored to fit the intraoperative findings. In the index case, however, the location and the encapsulated margin enabled us to get away with a Whipple's procedure with an unconventional excision.

Among resected cases, the survival rate for ACC in any stage has been described to be higher when compared with ductal carcinoma; relatively favorable at 25.1%, with a median survival time of 12 months from a series involving adult patients.[9] Our patient is doing well at 36 months of regular follow-up. The role of adjuvant therapy is doubtful and not established in these cases, with insufficient data and a lack of large-scale studies on it.[9]

In a pediatric ACC, surgical resection should always be attempted, and our case highlights that ACC arising from the head of the pancreas can be managed successfully without always resorting to a Whipple's procedure.

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Conflicts of interest

There are no conflicts of interest.