Spontaneous (Hashimoto-like) chronic lymphocytic thyroiditis in a rhesus macaque (Macaca mulatta)

A case of a female, 10-year-old rhesus macaque (Macaca mulatta) with spontaneous chronic lymphocytic thyroiditis is presented. At necropsy, the thyroid gland was slightly enlarged, with up to 2 mm large, round, confluent, beige foci on the surface of both lobes. Histopathologic features resembled human Hashimoto's thyroiditis: multifocally, the interstitium was infiltrated by lymphocytes and variably sized lymphoid follicles. In the pituitary gland, there were increased numbers of large, basophilic cells throughout the adenohypophysis. Using a human electrochemiluminescence immunoassay (ECLIA), no autoantibodies against thyroglobulin, thyroid peroxidase, or thyroid-stimulating hormone receptor were detected.