An aggressive malignant smooth muscle neoplasm, arising from the gallbladder. It is characterized by a proliferation of neoplastic spindle cells. The disease is Monarch Disease Ontology identifier MONDO_0003364 (gallbladder leiomyosarcoma). Also known as: gall bladder leiomyosarcoma, leiomyosarcoma of gall bladder, leiomyosarcoma of gallbladder, leiomyosarcoma of the gallbladder.