Sclerosing rhabdomyosarcoma: report of a case arising in the head and neck of an adult and review of the literature.

Sclerosing rhabdomyosarcoma is a unique rhabdomyosarcoma variant, characterized by a prominent hyalinizing matrix. A notable pitfall is the potential for the unusual matrix and often pseudovascular growth pattern of this lesion to lead to confusion with other sarcoma types, including osteosarcoma, chondrosarcoma, and angiosarcoma. Here we report a case of sclerosing rhabdomyosarcoma arising in a 40-year old male. The tumor was centered in the pterygomaxillary fossa with extensive infiltration into adjacent structures. Fine needle aspiration yielded a preliminary diagnosis of high-grade pleomorphic undifferentiated sarcoma, for which he received neoadjuvant chemotherapy and surgical resection. Microscopic examination showed a malignant spindled to round cell neoplasm with prominent osteoid-like, hyaline stroma. Focal rhabdomyoblastic differentiation and diffuse immunoreactivity for desmin and myogenin aided in diagnosis. Nineteen months status post primary resection, the patient expired with multiple lung and bony metastases. Among 39 cases reported thus far (including the present case), there is a broad age range (0.3-79 years), with an average age at presentation of 27 years. The most commonly involved sites are the extremities (n = 19) and head and neck (n = 15). Most cases have been treated by resection, often combined with radiation and/or chemotherapy. Out of 31 cases with follow-up information provided, 6 patients developed local recurrence, 7 patients developed regional or distant metastasis, and 5 patients died of disease. Herein we discuss the ongoing controversy regarding how sclerosing rhabdomyosarcoma might best fit into existing rhabdomyosarcoma classification schemes, based upon current clinicopathologic and molecular genetic evidence.