Expression of intermediate filaments in different human epithelial and mesenchymal tumors

Fifty primary gastrointestinal and breast carcinomas, four embryonal rhabdomyosarcomas, six nonmuscular mesenchymal malignant tumors and one mesothelioma have been studied to determine what type of intermediate filaments they express, using affinity purified antibodies to prekeratin, vimentin and desmin and FITC or peroxidase labeled second antibodies. The tissues were alcohol fixed and paraffin embedded before use. In all carcinoma cases the tumor cells are stained by antibodies to prekeratin, while the vimentin antibody only decorates the stroma. Prekeratin positive tumor cells are not only seen in well differentiated tumors, but also in signet ring cell carcinomas. In the case of rhabdomyosarcoma the tumor cells clearly were decorated by antibodies to desmin, while the vimentin antibody only stained very few tumor cells. In cases of nonmuscular mesenchymal tumors, the tumor cells could only be labeled by antibodies to vimentin and not by antibodies to prekeratin or desmin. In biphasic tumors like mesothelioma, different parts of the tumor were separated by antibodies to prekeratin and vimentin.