Solitary benign osteoblastic lesions of bone. Osteoid osteoma and benign osteoblastoma

Cases of osteoid osteoma, benign osteoblastoma, focal osteomyeitis and fibrous dysplasia have been studied. The first two are histologically indistinguishable except for size but are recognizable from fibrous dysplasia and related lesions. When osteoid osteoma and benign osteoblastoma are separated by the size of the lesion (smaller or larger than 1 cm), the skeletal distribution of each is different and different from fibrous dysplasia. Whether these differences imply different etiologies or merely reflect the influence of skeletal site on etiologically similar lesions cannot be settled, except in that focal osteomyelitis has no etiologic relationship to the others. The relationship between osteoid osteoma and benign osteoblastoma was studied in cases with serial roentgenograms. The former did not grow into the latter but sometimes grew larger, preserving the radiologic essentials of osteoid osteoma. The early phases of benign osteoblastoma were not elucidated. Axons have been demonstrated in four osteoid osteomas and the systematic search for nerves in benign osteoblastoma and fibrous dysplasia is advocated.