Two unusual variants of pancreatic neuroendocrine tumor and their potential pitfalls on fine‐needle aspiration cytology

Abstract

Endoscopic ultrasound-guided fine-needle aspiration is increasingly utilized for the diagnosis of pancreatic lesions. Although operator dependent, the procedure has good overall performance characteristics and is minimally invasive; however, accuracy and sensitivity are reportedly lower for pancreatic neuroendocrine tumor (PanNET) compared with the more common pancreatic ductal adenocarcinoma (pACA). The underperformance is further exacerbated by the unusual cases of PanNET presenting with variant cytomorphology. We report two separate diagnostically challenging cases: a pigmented PanNET and a clear cell PanNET. We briefly review the literature and emphasize the importance of recognizing these uncommon variants when encountered in aspirate material. Diagn. Cytopathol. 2017;45:371-378. © 2016 Wiley Periodicals, Inc.

Metastatic tumors to the pancreas, a 12‐year single institution review

“…The primary consideration in cases with known history of clear cell renal cell carcinoma is distinguishing metastases from the foamy gland variant of pancreatic ductal adenocarcinoma or clear cell variant of pancreatic neuroendocrine tumor. 8,11,12 Resolution of this differential diagnosis can be aided by a simple panel of immunohistochemical stains such as PAX8 and carbonic anhydrase IX.…”

Fibrous Extracellular Spheroids in an Endoscopic Ultrasound-Guided Pancreatic Fine Needle Aspiration Correlating to a Gyriform Pancreatic Endocrine Tumor with a Unique Cobblestone Pavement Growth Pattern

“…Cytological evaluation of FNA slides of nonfunctioning PanNETs most often confirms high cellularity, clean (non-necrotic) backgrounds and loosely cohesive, round to oval (sometimes plasmacytoid) repetitive cells with coarsely granular chromatin [1]. Importantly, rare cytologic variants of this rare tumor type including oncocytic variants, rhabdoid tumors, vacuolated examples, lipid-rich forms, and clear cell morphologies are known to exist [1, 9–12].…”

Morphologic Variants of Well-Differentiated Pancreatic Neuroendocrine Tumors: Fine-Needle Aspiration Cytomorphology and Diagnostic Pitfalls

“…The pigment is usually also present in the background, which is presumably caused by the dispersal of the pigment from ruptured cells during smearing. 15,16 The presence of brown-black pigment can easily raise the differential diagnosis of malignant melanoma, which is the most common pigmented neoplasm secondarily involving the pancreas. Malignant melanoma demonstrates overlapping cytomorphologic features with PanNETs, which include highly cellular aspirates, isolated-to-loosely cohesive cells, eccentric nuclei presenting with a plasmacytoid appearance, and occasional binucleated cells.…”