A leiomyoma, also known as a fibroid, is a benign smooth muscle tumor that very rarely becomes cancer (0.1%). They can occur in any organ, but the most common forms occur in the uterus, small bowel, and the esophagus. Polycythemia may occur due to increased erythropoietin production as part of a paraneoplastic syndrome. The word is from leio- + myo- + -oma, "smooth-muscle tumor". The plural form can be either the English leiomyomas or the classical leiomyomata. Uterus Uterine fibroids are leiomyomata of the uterine smooth muscle. As other leiomyomata, they are benign, but may lead to excessive menstrual bleeding (menorrhagia), often cause anemia and may lead to infertility. A rare form of these tumors is uterine lipoleiomyoma—benign tumors consisting of a mixture of adipocytes and smooth muscle cells. Uterine lipoleiomyomata have been observed together with ovarian and other pathologies and some of them may develop into liposarcoma. These tumors are monoclonal, and non-random chromosomal abnormalities have been seen in 40% of the tumors. Gallbladder Mesenchymal neoplasms of the gallbladder are rare and in particular leiomyomas of the gallbladder have been rarely reported, all of them in patients with immune system disorders. However, a case was reported in absence of associated immunodeficiency at Monash Hospital in Melbourne, Australia, in a healthy 39-year-old woman with no symptoms. Skin Leiomyomas of the skin are generally (1) acquired, and (2) divided into several categories: Solitary cutaneous leiomyoma Multiple cutaneous (or pilar) leiomyomas arising from the arrectores pilorum muscles Angioleiomyomas (vascular leiomyomas) that are thought to arise from vascular smooth muscle Dartoic (or genital) leiomyomas originating in the dartos muscles of the genitalia, areola, and nipple Angiolipoleiomyoma Esophagus, stomach and small intestines Leiomyoma is the most common benign mesenchymal tumor of esophagus and second most common benign tumor of the small bowel (with gastrointestinal stromal tumor as most common). Although leiomyoma is the most common benign esophageal tumor, malignant carcinoma is still 50 times more likely. Approximately 50% of cases are found in the jejunum, followed by the ileum in 31% of cases. Almost one half of all lesions are less than 5 centimeters. Other locations, metastatic leiomyoma Metastatic leiomyoma are an extremely rare complication after surgery to remove the uterus for uterine fibroids. The most frequent sites of occurrence are the lungs and pelvis. The lesions are hormonally responsive. Fibromyoma of the breast is an extremely rare benign breast neoplasm. Most reports in