Monarch Disease Ontology identifier MONDO_0003286 (extrahepatic bile duct leiomyoma) is a benign smooth muscle neoplasm arising from an extrahepatic bile duct. It is characterized by the presence of spindle cells with cigar-shaped nuclei, interlacing fascicles, and a whorled pattern. Also known as: leiomyoma of extrahepatic bile duct, leiomyoma of the extrahepatic bile duct.