[Pathologic-anatomic characteristics of benign bone tumors]

Benign bone tumors are frequently undiagnosed since they rarely cause pain. Based on the records of the Basle Bone Tumor Registry, which contains 2194 primary benign bone tumors, the aspects of benign bone tumors in childhood and adolescence are described. Benign bone-forming lesions like osteoid osteoma and osteoblastoma occur fairly frequently in this age group; osteofibrous dysplasia is almost exclusively seen in younger patients. Benign cartilage-forming tumors are much more cellular at this age and therefore sometimes misdiagnosed as chondrosarcomas. Chondromyxoid fibroma and especially chondroblastoma frequently occur in patients younger than 20 years. Because of their pleomorphic appearance (chondromyxoid fibroma) and their cellular composition and matrix deposition (chondroblastoma) they can be confused with chondrosarcomas, giant cell tumors or osteosarcomas. Benign fibrous histiocytoma is a very rare intraosseous fibrohistiocytic tumor that also can be found during adolescence. Since no one has much experience with this lesion, patients should be carefully monitored after complete excision. Giant cell tumors of bone reach their typical epimetaphyseal location after growth plate closure. If the physis is still open, giant cell tumors are almost exclusively found in a metaphyseal location abutting on epiphyseal cartilage. With increasing closure of the growth plate, the lesion is found most frequently in an epimetaphyseal position. The transition of a primary benign bone tumor to a sarcoma is very rare and often occurs in connection with irradiation treatment. The risk of a sarcomatous change independent of therapy is very infrequent.