Cardiac rhabdomyoma in a slaughtered pig

ABSTRACT: Rhabdomyoma is a rare neoplasm of striated muscle that occurs predominantly in the myocardium. In animals, cardiac rhabdomyoma are observed as incidental lesions in slaughter pigs and have been rarely described in other species, such as cattle, dogs, and deer. This report describes a case of cardiac rhabdomyoma in a male pig at slaughter age that died suddenly in the pre-slaughter period. At necropsy, multiple nodules were observed in the right and left ventricular walls and the interventricular septum. Histopathological examination showed neoplastic proliferation composed of polyhedral cells, with vacuolated cytoplasm that sometimes presented a “spider cell” appearance. Histochemical staining with Schiff’s periodic acid revealed glycogen granules in the cytoplasm of neoplastic cells. The neoplastic cells were positive for desmin, neuron-specific enolase, atrial natriuretic peptide, and vimentin by immunohistochemistry, to varying degrees. The anatomopathological and immunohistochemical findings observed in this case confirmed the diagnosis of cardiac rhabdomyoma, possibly originating from the Purkinje fibers.