Smooth muscle tumours of the uterus

Smooth muscle tumors of the uterus encompass a spectrum from benign leiomyomas (LM) to malignant leiomyosarcomas (LMS), with intermediate entities like Smooth Muscle Tumor of Uncertain Malignant Potential (STUMP). This paper reviews the pathological classification of uterine smooth muscle tumors, focusing on histological criteria and imaging appearances. We discuss atypical LM such as cellular, myxoid, bizarre nuclei, fumarase hydratase-deficient (FHD), and mitotically-active types as well as those with less common presentations, such as diffuse leiomyomatosis, intravenous leiomyomatosis, and benign metastasizing LM. Preoperative differentiation of these types of LM from LMS is important when considering morcellation as an adjunct to surgery. This paper includes a cohort of different case examples to help guide the reader. The review highlights the importance of combining morphological parameters such as tumor size, shape, clarity of margins, T1 and T2 signal heterogeneity, and functional MRI parameters such as signal on high b-value diffusion-weighted images, apparent diffusion coefficient values, and perfusion patterns to distinguish LM from LMS.