The authors report a case of metastasis of cancer from the breast in a uterine leiomyoma. The metastases into the body of the uterus from extragenital cancers are rare. If they occur they are usually in the myometrium where they are asymptomatic and where the diagnosis is difficult, or in the endometrium where the diagnosis can be made by biopsy after curettage. A few rare cases of metastases in uterine leiomyoma have been reported in the literature. They can be the cause of very sudden increase in size of fibroids with compression of the pelvic organs.