Uterine smooth muscle tumours with hyperintense area on T 1 weighted images: differentiation between leiomyosarcomas and leiomyomas

Objective: Hyperintense area on T 1 weighted images (T 1 HIA) have been reported as suggestive features of uterine leiomyosarcoma (LMS), but differentiating LMS from leiomyoma (LM) is often difficult. This study aimed to evaluate the differences between uterine LMS and LM demonstrating intratumoral T 1 HIA. Methods: MRI was performed in 509 patients with 1137 uterine smooth muscle tumours [14 LMSs, 5 smooth muscle tumours of uncertain malignant potential , and 1118 LMs] which exceeded 3 cm in diameter. LM with red degeneration and lipoleiomyoma were excluded from the study. We retrospectively reviewed the images and assessed T 1 HIA within tumours. Results T 1 HIAs were observed in 11/14 (78.6%) LMSs, 0/5 (0%) smooth muscle tumours of uncertain malignant potential, and 15/1118 (1.3%) LMs. T 1 HIAs were more homogenous (53 vs 0%, p < 0.01) and more well-demarcated (60 vs 9%, p < 0.05) in LMs than in LMSs. T 2 hypointense rim within T 1 HIA (53 vs 9%, p < 0.05) was more frequently observed in LMs than in LMSs. The occupying rate of T 1 HIA (0.20 ± 0.24 vs 0.42 ± 0.27, p < 0.05) was smaller in LMs than in LMSs. The signal intensity ratio of T 1 HIA (1.83 ± 0.36 vs 1.38 ± 0.23, p < 0.01) was greater in LMs than in LMSs. Conclusion: T 1 HIA within LM showed more homogeneity, better demarcation, smaller occupying rate, and higher signal intensity than T 1 HIA within LMS. Advances in knowledge: The differences in T 1 HIA within tumours may be useful for differentiating between LMS and LM.