Uterine tumour. Endoscope view of a leiomyoma (lump at lower centre) on a uterus (upper right). 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. An ovary (white/pink, upper left) is seen just above a Fallopian tube that runs to the left from the uterus. The two ovaries produce the eggs (ova, female reproductive cells) that pass to the uterus through the Fallopian tubes.