Monarch Disease Ontology id MONDO_0004125 (rectum leiomyoma) is a well-circumscribed benign smooth muscle neoplasm arising from the rectum. It is characterized by the presence of spindle cells with cigar-shaped nuclei, interlacing fascicles, and a whorled pattern. Also known as: leiomyoma of rectum, leiomyoma of the rectum, rectal leiomyoma.