Uterine tumour. Endoscope view of a hypotrophic (atrophied) uterus (upper centre) with a leiomyoma (rounded swelling) covering much of its visible surface. A leiomyoma is a benign muscle tumour (myoma). The term is used for benign tumours of smooth muscle, the uterus being one place where smooth muscle is found. A leiomyoma may become malignant, when it is termed a leiomyosarcoma, sarcoma referring to its cancerous nature. If a tumour is malignant or excessively large, it will need to be surgically removed. Structures leading off the uterus include ligaments that anchor it within the abdomen, and its two Fallopian tubes. This is the uterus of a menopausal woman.