A well-circumscribed benign smooth muscle neoplasm arising from the appendix. It is characterized by the presence of spindle cells with cigar-shaped nuclei, interlacing fascicles, and a whorled pattern. The disease is MONDO_0003300 (appendix leiomyoma). Also known as: appendiceal leiomyoma, leiomyoma of appendix, leiomyoma of the appendix, leiomyoma of vermiform appendix, vermiform appendix leiomyoma.