Intramuscular, extraskeletal mesenchymal chondrosarcoma.

Extraskeletal mesenchymal chondrosarcoma (EMC) is a rare and a malignant chondrogenic neoplasm. As a particularity of this neoplasm, about one-third of the cases develop outside the bone, with intramuscular site being a very rare location for development of EMC. The diagnosis of mesenchymal chondrosarcoma can be very challenging, especially in cases without conspicuous cartilaginous differentiation. In such cases its distinction from other small cell mesenchymal neoplasms cannot be safely established. This, however, is of major clinical interest as it implicates different treatment protocols as well as a different prognosis. We hereby present a case of EMC at a unusual location in a 23-year-old female with the purpose to highlight its morphologic features and to discuss its differential diagnosis.