The significance of cytoplasmic chondrocyte inclusions in multiple osteochondromatosis, solitary osteochondromas, and chondrodysplasias.

Lesions from two patients with multiple osteochondromas and from three patients with solitary osteochondromas were studied. The histologic and ultrastructural features in both conditions were identical. The chondrocyte population in osteochondromas resembled those in normal hyaline cartilage but the cells in osteochondromas exhibited an accumulation of granular and filamentous materials within markedly dilated cisterns of ergastoplasm. These accumulations formed eosinophilic cytoplasmic inclusions which did not stain with Alcian blue, but were PAS positive after diastase digestion. Chondrocytic inclusions of similar or diverse morphology are found in a number of chondrodysplasias. The findings suggest that the solitary osteochondromas, like the lesions of multiple osteochondromatosis, share a common morphologic feature with the chondrodysplasias.