Pancreatic endocrine tumor with partial acinar cell differentiation

Area of Science:

• Gastroenterology and Hepatology
• Endocrinology
• Surgical Pathology

Background:

• Pancreatic endocrine tumors (PETs) are neoplasms arising from the islet cells of the pancreas.
• While typically presenting with hormonal symptoms, some PETs can be non-functional or exhibit mixed differentiation.
• Acinar cell differentiation in PETs is uncommon, making such cases diagnostically complex.

Observation:

• A 70-year-old female patient presented with a large (12.5 x 9.5 x 8 cm) pancreatic tail tumor.
• The tumor was asymptomatic, lacking both endocrine and exocrine clinical manifestations.
• Gross examination revealed a capsulated, soft, medullary, yellowish-white mass with multiple nodules.

Findings:

• Histopathological analysis showed neoplastic cells with large, irregular nuclei and abundant eosinophilic cytoplasm.
• Tumor cells exhibited proliferation in various patterns, including islet-like, solid, trabecular, acinar, and papillary.
• Immunohistochemistry revealed strong synaptophysin positivity in most cells and alpha1-antitrypsin positivity in 10-25%.
• Ultrastructural examination confirmed the co-existence of neuroendocrine and zymogen granules within the same neoplastic cells.

Implications:

• The simultaneous presence of neuroendocrine and zymogen granules supports the classification of this tumor as amphicrine.
• This case highlights the importance of considering mixed differentiation in pancreatic neoplasms, even in asymptomatic patients.
• Understanding amphicrine tumors contributes to the broader knowledge of pancreatic cancer biology and potential therapeutic targets.