Assessment of proliferating-cell nuclear antigen immunostaining in soft-tissue tumours: relationship to histological grade and mitotic activity

Epithelioid Fibrous Histiocytoma of Bone

A benign fibrohistiocytic neoplasm of bone containing unique epithelioid cells is described in a 54-year-old man who presented with a well-defined lytic lesion in the left calcaneus. Curetted specimens showed microscopic evidence of proliferation of large plump, protoplasmic epithelioid or histiocytic cells with spindled to rounded shape, arranged in a storiform pattern, and osteoclast-like giant cells. This tumor did not show any specific immunoreactivity except for vimentin and actins. In addition to the basic ultrastructural characteristics of fibro/myofibroblasts, the large cells with abundant eosinophilic cytoplasm by light microscopy were shown to be packed with intermediate filaments of the vimentin type. Tumor was treated by curettage and bone grafting and showed radiolucent changes 1 year after operation but had not progressed 3 years later. The term epithelioid fibrous histiocytoma of bone is suggested for this previously undescribed variant of osseous fibrous histiocytoma Int J Surg Pathol 3(1):43-48, 1995