Rhabdomyosarcoma of the parapharyngeal space in an adult patient: an immunohistochemical study.

Rhabdomyogenic malignancies occasionally challenge the diagnostic acumen of many pathologists. The diverse histologic patterns of RMS can range from the somewhat undifferentiated primitive to the bizarre, pleomorphic varieties. These neoplasms can be highly lethal and, until recently, were resistant to even the most aggressive surgical management. The grave prognosis for patients with RMS has remarkably improved however, as a result of careful clinical staging, awareness of histologic features and immunohistochemical techniques for identification, newer techniques in defining the extent of the disease, and multimodal therapy consisting of surgery, radiation, and chemotherapy. Immunohistochemical methods with specific antibodies, as used in this case, have proved to be the only definitive method to identify this variant subclass of RMS.