Cercariform Cells: Another Cytologic Feature Distinguishing Solid Pseudopaillary Tumor (SPPT) from Pancreatic Endocrine Neoplasms (PEN) and Acinar Cell Carcinomas (ACC) in Endoscopic Ultrasound-Guided Fine Needle Aspirates (EUS-FNA)
Arbaz Samad, Akeesha A Shah, Edward B Stelow, Stuart E Cameron, Stefan E Pambuccian. University of Minnesota, Minneapolis, MN; University of Virginia, Charlottesville, VA
Background: SPPT is a rare tumor of unknown origin occurring predominantly in the body or tail of the pancreas in young women. We have recently identified cercariform (Greek: tailed) cells, similar to those described in urothelial carcinomas in a EUS-FNA of a SPPT. We performed a multi-institutional study to define the value of these cells in the differential diagnosis of SPPT with other neoplasms characterized cytologically by the presence of monotonous uniform cells in pancreatic aspirates (PEN and ACC).
Design: The files of 2 academic institutions were searched for SPPT, PEN and ACC diagnosed by EUS-FNA. The slides were reviewed and a number of cytologic features recorded semiquantitatively in order to identify discriminating features between SPPT, PEN and ACC.
Results: 15 cases of SPPT, occurring in 14F/1M aged 22-64 (mean=39) were identified, together with 4 cases of ACC in patients aged 50-75 (mean=63), 3F/1M. 15 cases of PEN were randomly selected from the files of 2 institutions. They occurred in 5F/10M aged 35-79 (mean=56). The tumors were located in the pancreatic tail (SPPT n=8, PEN n=5, ACC n=0), body (SPPT n=4, PEN n=4, ACC n=0) and head of the pancreas (SPPT n=3, PEN n=6, ACC n=4).The mean size (in cm) of the tumors was: 4.7 for SPPT, 2.8 for PEN and 3.8 for ACC. The following features were common to SPPT, PEN and ACC: moderate to abundant cellularity, single cells, cell groups (rosettes/acinar formations), round to plasmacytoid cells, necrosis, pale to granular cytoplasm with fine vacuoles and bilobed/binucleated cells. Differentiating features of SPPT are shown in table 1.
|Papillary structures||Cercariform cells||Large cytoplasmic vacuoles||Reniformnuc nuclei||Prominent nuclear grooves||Hyaline globuules/magenta-colored material||Degenerative features*|