Cardiac tumor comprising a malignant peripheral nerve sheath tumor and spontaneous atrial osseous metaplasia in a sheep.

Primary cardiac tumors in animals are very rare. The purpose of this report was to describe the first case of a cardiac tumor comprising a malignant peripheral nerve sheath tumor and spontaneous atrial osseous metaplasia in a Corriedale sheep. Histologically, the tumor in the bilateral atrial pericardium consisted of dense cellular components comprising tumor cells and a sparse cellular area, and non-neoplastic mature bone tissue. The tumor cells were spindle-shaped, round, or polygonal, and proliferating, with fascicular, storiform, palisading, and sheet patterns. Immunohistochemically, the tumor cells were positive for vimentin, S-100, occasionally positive for myeline basic protein, glial fibrillary acidic protein, neurofilament, neuron specific enolase, and neuron growth factor receptor suggesting that they originated from the nervous system. On the basis of these findings, the final diagnosis was a malignant peripheral nerve sheath tumor and spontaneous atrial osseous metaplasia.