A benign smooth muscle neoplasm arising from the pericardium. It is characterized by the presence of spindle cells with cigar-shaped nuclei, interlacing fascicles, and a whorled pattern. The disease is Monarch Disease Ontology identifier MONDO_0003294 (pericardium leiomyoma). Also known as: leiomyoma of pericardium, leiomyoma of the pericardium, pericardial leiomyoma.