[Ultrastructural and pathological studies of chondromyxoid fibroma of bone]

Histological and electron microscopic studies were carried out on a chondromyxoid fibroma in the right femur of a 8 years old boy. Although chondromyxoid fibroma contained chondroid, fibrovascular and myxoid components, the chondroid zone was transformed into myxoid zone through degeneration of chondroblastic tumor cells. Fibroblastic tumor cells gave no findings specific for fibroblast and fibrocyte on electron microscopy. Most primitive tumor cells were found in the fibromatoid zone. These cells have probably differenciated to fibroblastic and chondroblastic tumor cells. Histiocytes were gathered around the blood vessel. Despite the native of chondromyxoid fibroma as one of the bone tumor of cartilagenous deviation, it showed the characteristics of histiocytic tumors in part.