colon leiomyoma (Monarch Disease Ontology entry MONDO_0001092) is a well-circumscribed benign smooth muscle neoplasm arising from the colon. It is characterized by the presence of spindle cells with cigar-shaped nuclei, interlacing fascicles, and a whorled pattern. Also known as: colonic leiomyoma, leiomyoma of colon, leiomyoma of the colon.