Desmoplastic fibroma of bone with extensive cartilaginous metaplasia.

Desmoplastic fibroma of bone is a rare tumor demonstrating the same histologic and biologic features of its soft tissue counterpart, aggressive fibromatosis. We report the second case of desmoplastic fibroma of bone with extensive chondroid metaplasia. The tumor arose in the left ischium of a 51-year-old male, with extension into adjacent musculature as a pseudoencapsulated mass. The infiltrating growth and quality of the fibrous component are characteristic of desmoplastic fibroma, and in addition, abrupt transitions into bland hyalin cartilage were frequent. Discriminating features of this lesion from other bone tumors capable of biphasic expression of fibrous and chondroid elements are discussed.