Ultrastructure of synovial chondromatosis.

Electron microscopic examination in a case of synovial chondromatosis associated with moderate cytological atypia showed chondrocytes with abundant rough endoplasmic reticulum, prominent Golgi complexes, and peripheral aggregates of glycogen. These findings emphasize the similarity in ultrastructural appearance of chondromatosis, mature hyaline cartilage, and benign cartilaginous tumors and thus support the generally benign nature of synovial chondromatosis.