Objective: Hyperintense area on T1 weighted images (T1 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 T1 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 T1 HIA within tumours. Results T1 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. T1 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. T2 hypointense rim within T1 HIA (53 vs 9%, p < 0.05) was more frequently observed in LMs than in LMSs. The occupying rate of T1 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 T1 HIA (1.83 ± 0.36 vs 1.38 ± 0.23, p < 0.01) was greater in LMs than in LMSs.
Conclusion: T1 HIA within LM showed more homogeneity, better demarcation, smaller occupying rate, and higher signal intensity than T1 HIA within LMS. Advances in knowledge: The differences in T1 HIA within tumours may be useful for differentiating between LMS and LM.