Case report 713. Chondromyxoid fibroma of the third metatarsal.

In the case presented, the imaging features are those of an aggressive benign or less aggressive malignant lesion. The differential diagnosis radiographically included aneurysmal bone cyst with or without an accompanying lesion, giant cell tumor synovial sarcoma, and other mesenchymal sarcomas. Indeed, at times it is difficult to be certain whether the process originated in the bone or soft tissue. Pathological examination of the resected specimen showed the typical features of chondromyxoid fibroma. Grossly, the tumor was well demarcated and firm and composed of tan, translucent tissue that destroyed cortex but was confirmed by periosteum. Histologically, the tumor consisted of myxoid, chondroid, and fibrous elements. The tumor lobules were composed of predominately myxoid matrix containing stellate cells. Variable chondroid elements were present with immature appearing chondrocytes, containing eosinophilic cytoplasm and irregularly shaped nuclei.