MICROADENOCARCINOMA OF THE PANCREAS - MORPHOLOGIC PATTERN OR PATHOLOGICAL ENTITY - A REEVALUATION OF THE ORIGINAL SERIES

The term microadenocarcinoma was first proposed for a sub-type of panc reatic carcinoma by Cubilla and Fitzgerald in 1975 based largely on th e morphological features of 15 cases. Since that time, no independent studies have appeared in the English literature to address whether mic roadenocarcinoma represents a distinctive tumor or a pattern of growth , and some authors have questioned its existence as a definable entity . Immunohistochemistry is now available to allow the identification of lines of differentiation in pancreatic neoplasms, on which their clas sification is largely based. Reasoning that heterogeneity of different iation between different cases would not justify the separation of mic roadenocarcinomas from other better defined pancreatic neoplasms, we r eevaluated 12 cases from the original series using antibodies for acin ar, endocrine, and ductal differentiation. Two distinctive morphologic al patterns were identified: microglandular and solid cribriform. The microglandular cases (n = 6) were not separable from typical ductal ad enocarcinomas either morphologically or immunophenotypically. Of the s olid-cribriform cases (n = 6), immunohistochemistry revealed three to be acinar cell carcinomas, one an endocrine carcinoma, one a mixed end ocrine-ductal carcinoma, and one a ductal adenocarcinoma. We concluded that with the benefit of further study, most of these cases could be reclassified as other types of pancreatic carcinoma. Microadenocarcino ma is best regarded as a pattern of growth associated with an aggressi ve clinical course rather than a distinctive entity.