Unearthing the Unexpected: First Report of Ossa Cordis in a Human Heart.

The ossa cordis (OC), or cardiac bone, is a bony structure within the cardiac skeleton of mammals, believed to maintain heart shape during systole and enhance contraction efficiency. Found in large mammals, especially ruminants, and has recently been described in chimpanzees; however, OC has not previously been described in humans. Herein, we present an incidental finding of OC in the heart of a 39-year-old man who suffered a stab wound to chest. A thorough postmortem examination revealed a 0.8 × 0.6 × 0.4-cm, well-defined, boomerang-shaped, bony structure embedded in atrioventricular node location in the right atrium within the triangle of Koch. The heart showed cardiomegaly and moderate atherosclerosis in the left anterior descending and right coronary arteries but was otherwise normal, without fibrosis, valvular abnormalities, or degenerative changes. Histological analysis revealed mature bone with trilineage hematopoietic elements. This finding highlights anatomical similarities between human hearts and other species, raising questions about whether OC in humans and primates is linked solely to degenerative cardiac disorders or represents a normal aspect of mammalian heart development and aging. To our knowledge, this is the first reported case of an OC in a human.