A usually aggressive malignant neoplasm arising from the heart. It is characterized by the presence of spindle-shaped fibroblasts and collagenous stroma formation in a herringbone growth pattern. The disease is MONDO_0003742 (heart fibrosarcoma). Also known as: Cardiac fibrosarcoma, cardiac fibrosarcoma, fibrosarcoma of heart, fibrosarcoma of the heart, heart fibrosarcoma (disease).