Extraskeletal mesenchymal chondrosarcoma arising in adductor magnus with metastatic foci

Mesenchymal chondrosarcoma is a rare and aggressive chondrogenic neoplasm arising from the bone or the soft tissue. Mesenchymal chondrosarcomas develop outside the osseous structures in about one-third of cases, and the majority of these occur in the meninges and the brain parenchyma. Intramuscular extraskeletal mesenchymal chondrosarcoma (EMC) is exceedingly rare, with very few cases reported in the literature. Although mesenchymal chondrosarcoma has a high potential for metastasis, there have been no reports of pulmonary metastasis from an EMC of intramuscular origin. Here, we describe a patient who came to our facility with a history of progressively worsening left lower extremity pain and swelling, and was found to have pathology-proven EMC originating in the left adductor magnus, with complete workup demonstrating multiple bilateral pulmonary metastases in addition to a possible metastatic focus in the right adrenal gland discovered during the interval surveillance period.