Thallium-201 scintigraphy is an effective diagnostic modality to distinguish malignant from benign soft-tissue tumors

Background: The aim of this study is to evaluate whether thallium-201 (201-Tl) scintigraphy can differentiate malignant from benign soft-tissue tumors. Methods: Between April 1995 and December 2005, 192 patients with soft-tissue tumors (85 malignant and 107 benign) underwent 201-Tl scintigraphy before treatment. Isotope uptake was used as a proxy for tumor-to-background ratio (TBR). The accuracy of TBR on early and delayed imaging was evaluated using the Mann-Whitney U and χ ² tests. Results: There was a statistically significant difference in mean TBR on early and delayed imaging of malignant and benign soft-tissue tumors (124% ± 109% vs. 22% ± 42%, and 82% ± 83% vs. 12% ± 25%, P < 0.0001). A TBR cutoff of 20% indicated the probability of malignancy on early and delayed imaging (82% sensitivity and 77% specificity; 82% sensitivity and 84% specificity, P < 0.0001). Well-differentiated liposarcomas showed low isotope accumulation, while pigmented villonodular synovitis and giant cell tumors of the tendon sheath showed high isotope accumulation. Conclusions: Thallium-201 scintigraphy can distinguish malignant from benign tumors with relatively high accuracy. With the exception of low grade liposarcomas and locally aggressive benign tumors, 201-Tl scintigraphy may be an effective diagnostic modality to differentiate malignant from benign soft-tissue tumors.