[Diagnostic application of immunohistochemistry in pleomorphic sarcomas]

Eighteen cases of pleomorphic sarcoma diagnosed or supposed as rhabdomyosarcomas (RMS) and fourteen cases of other soft tissue lesions were stained with five specific antisera (myoglobin, desmin, alpha-1-antitrypsin, Lysozyme, and S-100) by peroxidase antiperoxidase method. The immunohistochemical findings indicated that the majority of the pleomorphic sarcomas (11/18) had to be reclassified as malignant fibrous histiocytoma (MFH), and pleomorphic RMS was indeed rare in adults over the age of 30 years. In this MFH group, desmin was present in all but 3 cases (8/11), supporting that MFH is a tumor originated from mesenchymal cells other than histiocytes. The success of using immunohistochemistry for making pathologic diagnosis depends upon rational application of panels of antibodies. The diagnostic features of pleomorphic sarcomas in routine or special stains are discussed.