[1461] A Clinicopathologic Study of Mixed Acinar Ductal Carcinomas of the Pancreas

EB Stelow, F Bao, NJ Nolan, R Shaco-Levy, J Garcia, DS Klimstra. University of Virginia, Charlottesville, VA; Memorial Sloan-Kettering Cancer Center, New York, NY; Ben-Gurian University, Beer-Shiva, Israel

Background: Pancreatic acinar cell carcinomas (ACCs) are clinically and pathologically distinct from pancreatic ductal adenocarcinomas (PDAs). Whereas endocrine differentiation has been well demonstrated in ACCs, significant ductal components are rare. This paper reviews the clinicopathologic features of a series of ACCs with prominent ductal differentiation.
Design: Cases of pancreatic ACCs with significant (>25% of the tumor) ductal differentiation were identied in the surgical pathology databases of two academic centers. Patient clinical information, gross and histologic features, and histochemical and immunohistochemical (IHC) results were recorded. Cases were tested for KRAS2 mutations.
Results: Ten cases were identified (8 men and 2 women; age range 52-77 yrs). Only 1 patient presented with jaundice. All but 1 patient were treated with primary surgery and most received adjuvant therapy. All but 1 patient with follow-up had died (dead of disease=8; 9-52 mo; ave= 26 mo). Tumors measured between 2 and 5.5 cm and were ill-defined, nodular and multilobulated. Nine were located in the head of the pancreas. All but 2 exhibited extrapancreatic invasion. In most cases (8), the acinar phenotype predominated (>50%), and the tumors were composed of nodules of neoplastic acinar cells growing in acini, trabeculae and nests. Between 10 and 75% of the neoplastic nodules contained variable amounts of extracellular mucus, focally appearing colloidal. Between 10 and 25% of the tumors cells had a mixed phenotype with granular cytoplasm displaced either by multiple, foamy vacuoles or, by a single large mucous droplet that compressed the nucleus and rendered a signet-ring cell appearance. Two cases had areas recapitulating typical PDAs while the other portions of the tumors appeared akin to the mucinous acinar cell pattern described above. All cases had intracellular and extracellular mucus by mucicarmine stain. IHC results were as follows: trypsin+ (100%), chymotrypsin+ (88%), CK19+ (100%), B72.3+ (50%), CA19.9+ (88%), synaptophysin+ (focal) (33%), and chromogranin+ (focal) (22%). Two cases had KRAS2 mutations.
Conclusions: Despite the early embryologic divergence of acinar and ductal cell lineages, rare pancreatic tumors have both acinar and ductal differentiation, usually predominantly the former. They produce mucin and express markers of both cell lineages. The clinical course is highly aggressive.
Category: Liver & Pancreas

Wednesday, March 11, 2009 9:30 AM

Poster Session V # 238, Wednesday Morning