Solitary osteochondroma of the clavicle.

There are no clinicopathologic reports of solitary osteochondroma of the clavicle other than listings in tumor registries. Two boys had solitary asymptomatic osteochondroma, in one at the medial and in the other at the lateral aspect of the clavicle. One underwent excision to correct cosmetic deformity. Several histologic and experimental studies have shown that osteochondromas originate from cells of the growth plate. During development of the clavicle, cartilage appears on both the medial and lateral aspects. Histologic studies have suggested that this cartilage is similar to a physeal growth plate. Experimental studies, however, have shown it to be a randomly organized secondary cartilage that develops in membranous bones once ossification has begun. The occurrence of an osteochondroma at the ends of the clavicle lends support to the theory that the cartilage at the ends of the developing clavicle functions as a growth plate.