Extraskeletal mesenchymal chondrosarcoma: case report.

This is a case report of an extraskeletal mesenchymal chondrosarcoma (ESMC) that originally occurred in the retroperitoneum of a 24-year-old female and later metastasized to the left proximal humerus. Mesenchymal chondrosarcomas are very rare in comparison to conventional chondrosarcomas and even more so when arising from an extraskeletal location. In this report, we discuss the major characteristics of ESMC and offer a review of the current knowledge regarding this rare disease entity.