False positive 18F-FDG PET in an ischial chondroblastoma; an analysis of glucose transporter 1 and hexokinase II expression.

We report a rare case of chondroblastoma arising from the ischium which showed an increased (18)F-FDG uptake. Chondroblastoma is an uncommon lesion and usually involves the epiphysis of long bones. However, in this case, the tumor appeared as a well-defined osteolytic lesion in the ischium on radiographs. MR imaging demonstrated two components in the tumor: a solid one and a multilobular cystic component. (18)F-FDG PET imaging revealed an increased uptake in the ischium. The (18)F-FDG uptake resembled the results observed in malignant bone tumors. A histological diagnosis of chondroblastoma was obtained from tissue of an open biopsy. An immunohistochemical analysis demonstrated weak expression of both Glut-1 and HK-II. These findings suggest that Glut-1 and HK-II expression are not strongly related to FDG uptake in chondroblastoma.