Extraskeletal myxoid chondrosarcoma: rare presentation in the knee joint space

Extraskeletal myxoid chondrosarcoma is a malignant cartilage tumor that rarely presents in the joint space. This article presents a case of a man who presented with a 1-year history of continuous growth of a mass over the medial aspect of his right knee. Radiographs demonstrated osteoarthritis, and arthroscopy was performed for degenerative joint disease. At the time of surgery, an intra-articular mass was encountered and an unplanned biopsy was performed. Pathological analysis revealed the mass to be a primary extraskeletal, intra-articular chondrosarcoma. He had no history of malignancy. He underwent extra-articular resection of the lesion and reconstruction with endoprosthesis. The patient's clinical course required multiple re-operations, and pulmonary metastases developed. A gastrocnemius flap was performed for wound coverage in proximity to the resected arthroscopy portals. This case emphasizes the importance of proper preoperative imaging and planning for lesion biopsies. Proper initial management may have led to lesser overall morbidity. Review of the literature reveals that this is the only reported case of a primary intra-articular extraskeletal myxoid chondrosarcoma.