Chromosomal translocation-negative cellular extraskeletal myxoid chondrosarcoma in an adolescent female.

Extraskeletal myxoid chondrosarcoma (EMC) is a relatively uncommon soft tissue sarcoma that typically presents in adults of middle age and affects the proximal thigh and limb girdles. Initially believed to be a low-grade malignancy, long-term patient follow-up has shown a high incidence of local recurrence and metastatic spread. EMC is uniformly resistant to chemotherapy and radiation therapy. These tumors characteristically display fibrous septae with large aggregates of mucin populated by clusters and strands of oval cells exhibiting minimal mitotic activity. A more aggressive cellular subtype has also been defined and exhibits basaloid cells showing the immunohistochemical staining features of neuroendocrine differentiation calling into question their proposed cartilaginous lineage. Most, although not all, examples of EMC possess a unique balanced chromosomal translocation [t(9;22)(q22;q12)] between the EWSR1 and NR4A3 (previously termed TEC) genes. Pediatric and adolescent cases of EMC are rare, as only 15 have been reported and appear to follow a more aggressive clinical course. Reported herein is a case of an EMC arising in the thigh of a 15-year-old female and the first to undergo evaluation of chromosomal translocation.