Tumor grade-related thallium-201 uptake in chondrosarcomas

Diagnosis of low-grade chondrosarcoma, especially discrimination between enchondroma and low-grade chondrosarcoma, may be difficult pathologically. The aim of this study was to evaluate the value of thallium-201 (Tl-201) scintigraphy in the diagnosis of chondrosarcoma and to investigate whether there was a correlation between Tl-201 uptake and tumor grade.

We retrospectively evaluated 121 patients with pathologically proven bone and soft tissue tumors diagnosed between the years 1999 and 2007. All patients were followed by the Bone and Soft Tissue Tumor Working Group in our hospital. Twenty-three patients, mean age 44 +/- 15 (range 17-72) years, with a diagnosis of cartilaginous tumors were included. Increased Tl-201 uptake at the lesion sites greater than background was evaluated as malignant tumor. For the pathologic classification, a grading system (grade 1-3) based on the histopathologic findings was used. Pearson correlation coefficient was used to determine whether there was any correlation between Tl-201 uptake and tumor grade in chondrosarcoma.

There were 7 enchondromas and 16 chondrosarcomas. Four of 16 patients with chondrosarcoma had lesions pathologically classified as grade 3, 5 as grade 2, and 7 had grade 1 chondrosarcoma. Increased Tl-201 uptake was observed in all patients with grade 3 chondrosarcoma and 2 patients with grade 2 chondrosarcoma. Of 10 patients with chondrosarcoma, 3 grade 2 chondrosarcomas and 7 grade 1 chondrosarcomas, there was no Tl-201 uptake in the tumor region. A significant correlation was found between Tl-201 uptake and tumor grade in chondrosarcoma (p = 0.002, r = 0.71). Only a few reports in literature have demonstrated false negative results in low-grade chondrosarcoma.

Tl-201 uptake was related to tumor grade in chondrosarcoma. If there is a possibility of chondrosarcoma, Tl-201 scintigraphy should be reported with caution.