Uses of antibody panels in the analysis of metastatic carcinomas of unknown primary

Immunohistochemical analysis can help determine the primary site of origin of carcinomas presenting at metastatic sites. Different types of epithelium, and their corresponding carcinomas, express different subsets of cytokeratins. Thus, antibodies to unique cytokeratins, such as "high molecular weight" cytokeratins, cytokeratin 7, cytokeratin 8, and cytokeratin 20, can help distinguish among different types of carcinomas that may have similar histologic appearances. Also helpful in this analysis are antibodies to the CEA family of proteins, as carcinomas of different sites vary widely in the quantitative and qualitative expression of these proteins. Another approach is the use of antibodies to vimentin, the intermediate filament protein that is co-expressed along with cytokeratin in a limited subset of carcinomas. Additionally, determination of primary site of origin of carcinomas can be assisted by the use of organ-associated markers such as prostatic specific antigen (prostate), gross cystic disease fluid protein-15 (breast), mesothelin (ovary, mesothelium), and thyroid transcription factor-1 (lung,thyroid). Selection of the appropriate subset of these antibodies can be most helpful in clinical situations where there is a limited set of possible primary sites (e.g., breast vs. lung or bladder vs, prostate).