Extraskeletal myxoid chondrosarcoma arising from the clavicle.

This report presents an extremely rare case of extraskeletal myxoid chondrosarcoma (EMC) arising from the clavicular periosteum. To the best of our knowledge, this may be the first detailed report of its clinicopathological findings. The patient was a 48-year-old man. Plain radiography and CT did not demonstrate any osteolytic lesion or periosteal reaction in the right clavicle. However, MRI showed an isosignal-intensity mass on T1-weighted images and a homogeneous high signal intensity lesion on T2-weighted images. The histological findings of the widely resected tumor were consistent with the diagnosis of extraskeletal myxoid chondrosarcoma. Preoperative diagnosis of extraskeletal myxoid chondrosarcoma at an unusual location, as in this case, is difficult not only with imaging examinations alone, but sometimes even after histological examination of biopsy specimens.