Abstract
Four aged retired Chinese native pigs, three females and one male, estimated as over 10-year-old, were subjected to autopsy because of infertility due to aging. Grossly, nodular lesions were found bilaterally in the adrenal medulla of all four pigs. Based on the gross and the histopathological findings, they were diagnosed as either medullary nodular hyperplasia or pheochromocytoma. Immunohistochemically, proliferating cells of all these lesions were immuno-positive for chromogranin-A, indicating adrenal medulla-derived. Ultrastructurally, cytoplasmic neurosecretory granules suggestive of secretion were observed in these proliferating cells. There have been only limited numbers of reports on adrenal medullar proliferative changes including pheochromocytoma in pigs. The present cases will provide a valuable information for the characterization of similar changes in animals and human.