A 24-year-old woman with a history of heavy and painful menstrual periods has been having difficulty conceiving despite months of trying to become pregnant. Fuher workup includes a bimanual pelvic examination and an ultrasound, which demonstrates a mass in the uterus that is presumed to be a leiomyoma. This mass is a

A leiomyoma (fibroid) is a benign tumor of the smooth muscle of the uterus and thus is an example of a benign tumor of mesenchymal origin. Profuse, painful menses and infeility are major complications of this most common tumor of the female genital tract. A leiomyosarcoma is the malignant counterpa. Malignant tumors of epithelial cells are carcinomas, and these are known as Adenocarcinomas if they involve glandular epithelium. Benign tumors of surface epithelium are termed papillomas