Immunochemical demonstration of keratin and vimentin in cytologic aspirates.

Antibodies to intermediate filament proteins were used to characterize tumor cells present in peritoneal and pleural effusions and in thin needle aspirates from palpable lymph nodes. Metastatic adenocarcinoma cells (breast, ovary, endometrium, cervix, colon and stomach) as well as squamous-cell carcinomas and mesotheliomas stained specifically with antibodies to keratin while mesenchymally derived tumor cells (lymphomas, melanoma, fibrosarcoma and neurofibrosarcoma) were positive only for vimentin. Especially in cases of lymph node aspirates, keratin staining in cells was a direct indication of metastatic carcinoma. Antibodies to these different components of the cytoskeleton can thus be used in cytopathologic diagnosis when a definitive diagnosis cannot be made on the basis of conventional cytologic features.