Soft tissue osteochondroma: case report and immunohistochemistry for parathyroid hormone-related protein.

Surface lesions of bone usually present little diagnostic dilemma because the majority are conventional osteochondromas. Other surface bone lesions include periosteal chondroma, periosteal chondrosarcoma, and parosteal osteosarcoma. Mineralized soft tissue lesions such as myositis ossificans, synovial chondroma, and synovial sarcoma may present in a similar fashion when they occur in a juxtaarticular position. The soft tissue osteochondroma or paraarticular osteochondroma may simulate some of these more aggressive tumors, and its recognition is important to avoid overtreatment. A case of an 11-year-old male with a soft tissue osteochondroma is reported to illustrate the characteristic radiographic and histological features of this rare entity. No prior reports have examined soft tissue osteochondroma for expression of parathyroid hormone related protein, an established cartilage tumor proliferative mitogen.