[Immunohistochemical differential diagnosis of 60 cases of rhabdomyosarcoma]

Using the avidin-biotin complex immunoperoxidase technique and antibodies to myoglobin, desmin, CLA, NSE, GFAP, keratin, fibronectin, alpha 1AT, lysozyme, S-100 protein, vimentin, cytokeratin, actin, the authors studied 60 cases of rhabdomyosarcoma (RMS) histopathologically diagnosed previously. Thirty-six cases showed both myoglobin and desmin positive stain, an objective evidence of the origin from skeletal muscles. The other 24 cases were identified as of non-skeletal muscle origin, including MFH, lymphoma, melanoma, neuroblastoma, malignant neurilemmoma, leiomyosarcoma etc. This study strongly suggests that histologic examination of RMS may lead to incorrect diagnosis. Histologically MFH and other types of spindle cell sarcomas invading normal skeletal muscles may be confused with pleomorphic RMS, lymphoma and neuroblastoma may be confused with embryonic RMS. Our findings indicate that myoglobin is a highly sensitive and specific tumor marker for RMS.