Anatomic Pathology / CYTOLOGY OF PANCREATIC FOAMY GLAND ADENOCARCINOMA The Cytology of Pancreatic Foamy Gland Adenocarcinoma

All cell block specimens from pancreatic fineneedle aspirations (FNAs) obtained between January 1, 2002, and June 30, 2003, were reviewed for foamy gland adenocarcinoma (FGA). All smears from these cases were reviewed for cytologic features, including those previously noted in conventional pancreatic adenocarcinoma. Fifty-two cell block specimens showed adenocarcinoma. Of these, 12 (23%) showed histologic features of FGA. This pattern predominated in 6 cases and was present focally in 6 cases. Although there were relatively low nuclear/cytoplasmic (N/C) ratios, other features of adenocarcinoma were present universally, including loss of cohesiveness, nuclear overlap or loss of “honeycomb” architecture, anisonucleosis (>4 to 1), irregular nuclear contours, prominent nucleoli, and atypical chromatin. Background necrosis was present in 8 cases. Distinct cell borders were present in 9 cases, and foamy cytoplasm was present in all cases. Pancreatic FGA is a recently described histologic pattern of pancreatic adenocarcinoma. It is not uncommon, and we identified the pattern, at least focally, in 23% of our FNA cell blocks. Although cytologic samples show low N/C ratios, most cytologic features of conventional pancreatic adenocarcinoma are present, and the diagnosis presents little additional difficulty. The use of endoscopic ultrasound (EUS) has facilitated sampling of pancreatic lesions by fine-needle aspiration (FNA).1-5 Although the features of usual pancreatic ductal adenocarcinoma (PDA) have been well described, occasional cases might present diagnostic challenges.6-9 The foamy gland pattern of PDA (foamy gland adenocarcinoma [FGA]) is a recently described histologic pattern characterized by cells with abundant clear, “microvesicular” cytoplasm; basally located, irregular, hyperchromatic nuclei; and a brush border–like zone created by apparent apical cytoplasmic condensation.10 The pattern seems to have no clinical or biologic relevance in and of itself; however, owing to its somewhat bland appearance, it can present diagnostic challenges histologically, especially with small biopsy specimens. To assess whether these same difficulties affect cytologic interpretation, we searched for all cases of FGA present in cell block sections from pancreatic FNA at our institution. We then evaluated the cytologic features of 12 consecutive cases. Materials and Methods EUS was performed by the usual methods. Pancreatic FNA was performed with 22and 25-gauge needles. Airdried, rapid Romanowsky–stained slides; ethanol-fixed, Papanicolaou-stained slides; and formalin-fixed, paraffinembedded cell blocks were prepared at the discretion of the pathologist attending the procedure (E.B.S., R.H.B., S.M.D., or M.W.S.). Cell blocks were made by permitting aspirated material to clot on a slide and then scraping it into 10% buffered formalin. This material then was Am J Clin Pathol 2004;121:893-897 893 893 DOI: 10.1309/CJ9EF3XFXWQ3W82T 893 © American Society for Clinical Pathology Stelow et al / CYTOLOGY OF PANCREATIC FOAMY GLAND ADENOCARCINOMA processed by routine histologic methods, and H&E-stained sections were made. All slides from pancreatic FNA cell blocks made between January 1, 2002, and June 30, 2003, were reviewed. All cases with the histologic features of FGA were identified (criteria used were those described by Adsay et al10 and included all of the following: cells with abundant clear microvesicular cytoplasm; basally located, irregular, hyperchromatic nuclei; and a brush border–like zone created by apparent apical cytoplasmic condensation). It was noted whether the foamy gland pattern predominated (>50% of total malignant tissue) or was a minor component of the overall histologic features (<50% of total malignant tissue). All cytologic slides from cases with FGA were reviewed for cytologic features of conventional PDA, including the following: (1) loss of “honeycomb” architecture or nuclear overlap, (2) anisonucleosis (>4 to 1), (3) irregular nuclear contours, (4) prominent nucleoli, (5) clumped chromatin, (6) background necrosis, and (7) cellular discohesion. Foamy cytoplasm, nuclear/cytoplasmic ratios, and the presence of prominent cytoplasmic borders also were noted.