[Clinicopathological analysis, immunohistochemical study and electron microscopic observation of chondroblastoma of bone].

A series of 73 cases of chondroblastoma of bone, a rare benign tumor, was subjected to clinicopathological analysis, 50 cases of it were studied by immunohistochemistry and affinity histochemistry and 3 cases were observed by electron microscopy. In this series, chondroblastomas were found nearly in patients of all age groups, with the peak incidence occurring in the second decade of life. The lesions were more commonly located in long bone metaphyseal portion, especially in the upper end of femur and the head and neck of femur. It was easily misdiagnosed as giant cell tumor of bone, chondroma, and osteochondroma by clinic and radiography. There was gradual transition from a few chondroblasts to a small focus of clear cells in 3 cases, therefore, chondroblastoma may transform into clear cell chondrosarcoma by anaplastic change of chondroblast, which is one of malignant chondroblastomas. Our immunohistochemistry and affinity histochemistry results supported the point of view of chondroblast originated from epiphyseal chondrocytes. Immunohistochemical assessment of S-100 protein may be one useful parameter for differentiating chondroblastoma from giant cell tumor of bone and aneurysmal bone cyst ultrastructurally, chondroblasts had characteristic lobulated nuclei, compact zones under nuclear membrane, and microvilli on cells surface. In most cells, the Golgi apparatus and RER were inconspicuous without.