Cartilaginous membranocystic lesions mimicking membranous lipodystrophy of bone.

Two cases are presented in which membranocystic lesions were observed in the cartilaginous tissue of surgical specimens. In both cases, the histological and ultrastructural features were reviewed, and S-100 protein distribution was examined immunohistochemically in one case. In both cases, the membranocystic lesions were observed to be adjacent to ballooned chondrocytes. In one case, several chondrocytes showed partially membranocystic lesions in their cytoplasm. The chondrocytes and nuclei in membranocystic lesions were stained positively for S-100 protein. It is suggested that the membranocystic lesions in the cartilaginous tissue were associated with the degeneration of the chondrocytes.