Cell marker studies in undifferentiated soft tissue sarcoma

100 cases of undifferentiated soft tissue sarcomas were studied using cell markers by immunoperoxidase technique with DAB as substrate. Vimentin, Desmin, Myoglobin, Actin, Keratin, Epithelial Membrane Antigen, S-100 protein, F VIII R Ag, A1 Antitrypsin, A1 Antichymotrypsin, Collagen-IV and UEA-1 lectin were used as markers. Fibrosarcoma was consistently positive for Vimentin and Collagen-IV. The undifferentiated Rhabdomyosarcoma showed strong and consistent positivity for Vimentin Actin and Myoglobin. Desmin positivity was the hallmark of leiomyosarcoma, whereas the malignant schwannomas were identified by their S-100 positivity. This marker along with A1AT and A1ACT reactivity was of great use in the identification of malignant fibrous histiocytoma. Angiosarcoma/malignant haemangioendothelioma could be identified with great accuracy by their strong positivity for F VIII RAg and UEA-1 lectin. Other miscellaneous sarcomas also could be identified by their specific reactivity to the markers used. We consider immunohistochemistry to be an important and essential adjunct to routine stains in the diagnosis of undifferentiated soft tissue sarcomas.