A leiomyoma (plural is 'leiomyomata') is a benign smooth muscle neoplasm that is very rarely (0.1%) premalignant. They can occur in any organ, but the most common forms occur in the uterus, small bowel and the esophagus.
Read more about Leiomyoma: Etymology, Uterine Leiomyomata, Esophageal, Cutaneous, Leiomyoma of Jejunum, Other Locations, Metastatic Leiomyoma