Extra skeletal myxoid chondrosarcoma of the ankle with pulmonary metastasis. Case report and a brief review of the literature

Extra skeletal chondrosarcoma is a collective term for a group of malignant tumors that are not directly related to the bone or cartilage and is a diverse category. Primary chondrosarcomas typically arise in the skeleton, with a minority developing in an extra skeletal setting, which introduces challenges in diagnosis and classification. Of these, two entities are well-defined and characterized: extra skeletal myxoid chondrosarcoma (EMyC) and extra skeletal mesenchymal chondrosarcoma (EMC). While both are rare, they differ in their morphology and behavior, having little in common besides the myxoid matrix and soft tissue origin. EMyC has a wide differential diagnosis, including benign and malignant tumors. The rarity of EMyC poses a significant diagnostic challenge, both radiologically and pathologically. We report the case of a 29-year-old healthy man who sought advice from his family doctor regarding a lump that had formed on his left ankle for almost a year. Imaging studies, tissue histomorphology, and immunohistochemical (IHC) studies supported the diagnosis of EMyC. The diagnosis was confirmed by the identification of the EWSR1-NR4A3 fusion gene through fluorescence in situ hybridization. The patient was treated with wide local excision and adjuvant radiotherapy. At 19 months postoperatively, three pulmonary metastases were found and effectively resected. At 26 months post metastasectomy, he remained asymptomatic with no recurrence. This case underscores the necessity of correlating radiologic, histologic, immunohistochemical, and molecular features for a definitive diagnosis of EMyC. It highlights the late metastatic potential of the tumor in the absence of metastases at presentation and after complete resection. Long-term follow-up is essential for monitoring patients with EMyC.