Lipid-rich variant of pancreatic endocrine neoplasms: a case report

Pancreatic endocrine neoplasms (PENs) are a well-defined and well-characterized group of tumors. We report a rare variant of PENs called a lipid-rich variant and elaborate on its cytologic features with reference to fine needle aspiration (FNA).

The patient was a 74-year-old man with a 2.1-cm mass in the body of the pancreas. The FNA showed numerous cells with vacuolated, foamy cytoplasm, mostly arranged individually but also in some apparently cohesive clusters. The nuclei were quite uniform. Many of the cells had the appearance of histiocytes. The cells in the cell block were immunoreactive (positive) for cytokeratin AE1/AE3, synaptophysin, and chromogranin A. Some admixed histiocytes stained for CD68. A diagnosis of PEN was made, with a suspicion for lipid-rich variant. An elective resection of the tumor was performed, which confirmed the diagnosis of lipid-rich variant of PENs. Lipid-rich variant of PENs can present a diagnostic dilemma on FNA.

Its mimickers include adrenal cortical carcinoma, metastatic clear-cell renal cell carcinoma, clear-cell PEN, foamy gland pattern of pancreatic ductal carcinoma, solid pseudopapillary tumor, and acinar cell carcinoma. The distinguishing morphologic and immunohistochemical features of each are described.