Microadenocarcinoma of the Pancreas— Morphologic Pattern or Pathologic Entity?

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Abstract
The term microadenocarcinoma was first proposed for a subtype of pancreatic carcinoma by Cubilla and Fitzgerald in 1975 based largely on the morphological features of 15 cases. Since that time, no independent studies have appeared in the English literature to address whether microadenocarcinoma represents a distinctive tumor or a pattern of growth, and some authors have questioned its existence as a definable entity. Immunohisto-chemistry is now available to allow the identification of lines of differentiation in pancreatic neoplasms, on which their classification is largely based. Reasoning that heterogeneity of differentiation between different cases would not justify the separation of microadenocarcinomas from other better defined pancreatic neoplasms, we reevaluated 12 cases from the original series using antibodies for acinar, endocrine, and ductal differ-entiation. Two distinctive morphological patterns were identified: microglandular and solid cribriform. The microglandular cases (n = 6) were not separable from typical ductal adenocarcinomas either morphologically or immunophenotypically. Of the solid-cribriform cases (n = 6), immunohistochemistry revealed three to be acinar cell carcinomas, one an endocrine carcinoma, one a mixed endocrine-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. Microadenocarcinoma is best regarded as a pattern of growth associated with an aggressive clinical course rather than a distinctive entity.