Breast Metastasis of Extraskeletal Myxoid Chondrosarcoma: A Case Report

Objective: Rare disease Background: Extraskeletal myxoid chondrosarcoma is a unique and distinct clinicopathological entity in terms of its origin, morphology, and biologic behavior. Despite being a slow-growing tumor, it has a high rate of local recurrences and history of metastases to uncommon sites like the mandible, liver, retroperitoneum, right ventricle, pancreas, and central nervous system. Here, we report a very unique case of extraskeletal myxoid chondrosarcoma that metastasized to the breast, which itself is a very rare site for metastases. Case Report: A 58-year-old woman presented with a large, firm, and tender soft-tissue mass (6.0x7.0 cm) underneath the sole of the left foot. A computerized tomography (CT) scan showed a heterogeneous lobulated mass in the plantar aspect of the forefoot, measuring 8.6x8.0x7.1 cm. Punch biopsies revealed histology consistent with extraskeletal myxoid chondrosarcoma. Metastatic work-up was negative. The mass was fully resected with left below-knee amputation. The histology of the resected mass was consistent with extraskeletal myxoid chondrosarcoma. A follow-up CT showed a new right breast nodule along with metastases to lung and bones. The results of the core needle biopsies of the right breast masses seen on mammogram were morphologically identical to extraskeletal myxoid chondrosarcoma. Conclusions: Although rare, metastases to the breast should be considered in the differential diagnosis of a breast mass. A close long-term follow-up is needed due to the unpredictable behavior of extraskeletal myxoid chondrosarcoma and the high frequency of local recurrences, metastases, and death due to disease.