Antemortem magnetic resonance imaging examination of an intracardiac bony mass in a cynomolgus monkey (Macaca fascicularis).

Ectopic ossification is defined as bone formation at a site where no bone tissue typically exists and usually presents a trabecular bone structure. Rare cases of ectopic ossification in cardiac masses have been previously reported. In general, cardiac masses are diagnosed by echocardiography, computed tomography, and magnetic resonance imaging (MRI). MRI, in particular, has been used in studies to evaluate cardiometabolic function and tumors in various non-human primates (NHPs). Here, we report a 15-year-old male cynomolgus monkey with significant weight loss and arrhythmia observed during a routine checkup. This is the first report of a cynomolgus monkey in which a cardiac mass with bone metaplasia in the right ventricle was confirmed by echocardiography, radiography and MRI before death.