Tumor immunophenotype: comparison between primary neoplasm and its metastases.

Monoclonal antibodies (MAb) are firmly established diagnostic adjuvants both in vitro and in vivo. Their potential for immunotherapy is highly promising. Antigenic heterogeneity of cells within the same tumor is a well known phenomenon; however, no large-scale studies are available to ascertain to what degree metastases maintain the immunophenotype of the primary tumors. For that purpose, we studied 54 commonly epithelial malignancies using immunohistochemistry (IHC) with a panel of seven frequently used MAb recognizing a gamut of membrane and cytoplasmic antigens (AE-1, CAM 5.2, B72.3, MC10, anti-carcinoembryonic antigen (anti-CEA), epithelial membrane antigen (EMA), and human milk fat globule (HMFG)). The number of metastases per primary tumor ranged between 1 and 26, with a total of 344 tissues studied. Metastases were located in regional and distal lymph nodes as well as in a diversity of organs (pancreas, adrenal, colon, spleen, soft tissues, etc). Only those cases in which all the tissues were obtained from a single surgical procedure and, therefore, uniformly fixed and processed, were selected. All the metastases from three cases (5.5%) were found to express one or two antigens not present on their primary. In no case did all metastases from a positive primary become negative for one MAb. Twelve cases (18.5%) showed modifications of the phenotype in one or more metastases. This study demonstrates that a broad phenotypic variation does not follow when tumors metastasize, and that it is, therefore, safe to foretell the metastatic immunophenotype based upon that of the primary tumor.