Clear cell variant of solid pseudopapillary neoplasm of pancreas diagnosed by fine needle aspiration: A case report and review of the literature
A 22-year-old woman was admitted to the hospital for abdominal pain. Ultrasonogram showed a solid/cystic mass, 2.6 cm in diameter, in the tail of the pancreas. Percutaneous ultrasound-guided fine needle aspiration biopsy (FNAB) was performed using a 22-gauge needle. Rapid onsite evaluation was performed using Diff-Quik-stained smears. Additional smears were fixed in ethanol and stained by the Papanicolaou method. The excess material was fixed in an alcohol-formalin solution for cell block preparation and paraffin sections were stained by hematoxylin and eosin. Immunocytochemical stains were performed on cell block sections.\nThe material was highly cellular and consisted of a monotonous population of loosely cohesive small to medium-sized, round to cuboidal epithelioid cells exhibiting high nuclear/cytoplasmic ratio, finely granular “salt and pepper” chromatin and nuclear grooves. Pseudopapillary structures with arborizing capillaries and metachromic core on Diff-Quik-stained smears were lined by epithelioid cells. Acinar and rosette-like formations, as well as single neoplastic cells were observed []. The background was clean, but scattered foamy histiocytes were present. Many tumor cells exhibited single or multiple clear cytoplasmic vacuoles, displacing the nucleus [Figures and ]. The vacuoles were well-defined and variable in size, producing coin-shaped empty spaces in the cytoplasm [Figures and ]. Necrosis and mitosis were not seen. Coin-shaped vacuoles were mimicking signet-ring appearance on the cell-block [Figures and ]. Periodic acid-schiff (PAS) and mucicarmine stains were negative on the cell block sections.\nTumor cells showed strong nuclear staining for β-catenin and cytoplasmic staining for vimentin and CD10 [Figures –]. The stains were negative for chromogranin A, synaptophysin and cytokeratin.