Uterine leiomyoma, light micrograph. Leiomyoma (fibroid) of the uterus is an extremely common benign smooth muscle tumour. It is seen in nearly 40% of women above the age of 50 years. They may be multiple and can become massive in size. They can cause abnormal uterine bleeding, interfere with pregnancy, result in chronic inflammation, or compress the ureters and produce urinary symptoms. This image shows a cellular leiomyoma which, as the name implies, shows markedly increased cellularity compared to the usual leiomyomas but no necrosis, cytologic atypia, or increased mitotic activity.