Immunohistologic evaluation of metastatic carcinomas of unknown origin: Analgorithmic approach

Pathologists are now asked frequently to determine the primary she for meta static carcinomas of unknown origin (MCUO), using adjunctive morphological techniques such as electron microscopy, immunohistology, and other modaliti es. The authors present an algorithmic immunohistochemical approach to this problem that is based on their experience with over 2,800 routinely-proces sed epithelial malignancies of various types. These have been studied with antibodies to keratins, vimentin, epithelial membrane antigen, MOC-31, tumo r associated-glycoprotein-72 (recognized by monoclonal antibody B72.3), pro state-specific antigen, thyroglobulin, gross cystic disease fluid protein-1 5, carcinoembryonic antigen, CA-125, CA19-9, placental alkaline phosphatase , S100 protein, and estrogen receptor protein. The algorithm that is struct ured around these 14 analytes is based on the relative predictive value of each marker, which in turn, determines its place in the sequence of interpr etation. The authors' experience with this approach shows 67% accuracy with regard to the ultimately determined site of origin for MCUO, a figure whic h is similar to that reported by other investigators. Copyright (C) 2000 by W.B. Saunders Company.