Characterization of cartilaginous tumors with ²⁰¹Tl scintigraphy

Histological diagnosis and grading of cartilaginous tumors are closely correlated with patient prognosis; consequently, they are essential elements. We attempted to clarify the characteristics of ²⁰¹Tl uptake in various histological types of cartilaginous tumors and to assess its clinical value. Methods: Twenty-two cases with histologically proven cartilaginous tumors (3 enchondromas, 15 conventional chondrosarcomas (grade I = 9, II = 5, III = 1), 3 mesenchymal chondrosarcomas, and 1 de-differentiated chondrosarcoma) were examined retrospectively. Planar ²⁰¹Tl images were recorded 15 min following intravenous injection of ²⁰¹Tl (111 MBq). ²⁰¹Tl uptake in the tumor was evaluated visually employing a five-grade scoring system: 0 = no appreciable uptake, 1 = faint uptake above the background level, 2 = moderate uptake, 3 = intense uptake but lower than heart uptake and 4 = uptake higher than heart uptake. Results: ²⁰¹Tl uptake scores were 0 in 3 of 3 enchondromas, 9 of 9 grade I, and 4 of 5 grade II conventional chondrosarcomas. ²⁰¹Tl uptake scores were 1 among 1 of 5 grades II and a grade III conventional chondrosarcoma. Mesenchymal chondrosarcoma and de-differentiated chondrosarcoma displayed ²⁰¹Tl uptake scores of 2 or 3. Conclusions: Absence of elevated ²⁰¹Tl uptake in cartilaginous tumors was indicative of enchondroma or low-grade conventional chondrosarcoma. However, in instances in which ²⁰¹Tl uptake is obvious, high-grade chondrosarcoma or variant types should be considered.