[Chondroblastoma occurring in atypical sites].

Objective: To study the clinical, pathologic and radiologic features of chondroblastoma occurring in sites other than epiphysis and apophysis of long bones, and to investigate possible reasons for misdiagnosis.

Methods: The clinical, pathologic and radiologic data of 18 chondroblastoma cases occurring in atypical sites were collected from 5 major hospitals in Shanghai during the past 12 years. S-100 immunostaining was performed to confirm the cartilaginous differentiation of the tumor cells.