Primary malignant myoepithelioma of the distal femur

Abstract

A 55-year-old male presented with a 1-month history of localized pain caused by an osteolytic and destructive lesion in the right distal femur. Histologically, the tumour consisted of spindle cells intermingled with epithelioid eosinophilic cells arranged in small cords embedded in a hyalinized-to-chondromyxoid stroma. Electron microscopy and immunohistochemistry showed features of myoepithelial differentiation. RT-PCR failed to demonstrate chimeric transcripts of extraskeletal myxoid chondrosarcoma. The final diagnosis was primary malignant myoepithelioma of bone. The patient is alive with lung metastases 13 months after surgery. Primary malignant myoepithelioma of bone is an exceptionally rare neoplasm that should be considered in the differential diagnosis with the more aggressive myxoid spindle cell sarcomas.