Subcutaneous sacrococcygeal myxopapillary ependymoma. A clinicopathologic study of 32 cases.

A clinicopathologic investigation was performed on 32 cases of myxopapillary ependymoma occurring as a primary tumor of the skin and subcutaneous tissue of the sacrococcygeal area. The tumor usually presented as an asymptomatic mass at the base of the spine in young individuals. Pilonidal cyst was the most frequent clinical diagnosis. The excised tumors often "shelled out" easily and none was adherent to the vertebral column or spinal cord structures. The tumors were circumscribed and located in the subcutaneous tissue and deep dermis. Microscopically, ultramicroscopically, histochemically, and immunohistochemically, the cutaneous myxopapillary ependymomas showed distinct changes. Follow-up data were available for 23 patients with a median follow-up interval of 7 years. Six patients were followed for 15 years or longer. Metastases occurred in four patients, an incidence of 17%.