Retrobulbar adenocarcinoma in an Amazon parrot ( Amazona autumnalis )

Abstract

Retrobulbar neoplasms are not common in mammals and are even more infrequently seen in nonmammalian species. The current report describes a retrobulbar mass creating exophthalmia and neurologic signs in a red-lored Amazon parrot ( Amazona autumnalis). A 27-year-old female parrot presented for a 3-day history of anorexia and a 2-week history of periocular soft tissue swelling and exophthalmia of the right eye. Physical examination revealed 9% dehydration and right eye exophthalmia with inability to retropulse the globe. A fine-needle aspirate was performed, and cytologic evaluation revealed necrotic debris with scattered clusters of epithelial cells, moderate numbers of macrophages, and few heterophils. Given the possibility of neoplasia and paucity of treatment options, the owners elected euthanasia and submitted the body for necropsy. A large, fluctuant, friable, red, retrobulbar mass with multiple areas of hemorrhage, on cut surface, was noted at necropsy. Histologically, the mass was composed of neoplastic, cuboidal to columnar epithelial cells, forming rosette-like glandular structures, admixed with abundant necrotic debris. The neoplastic cells were strongly positive for cytokeratin (AE1/AE3) by immunohistochemistry. Based on histopathology and immunohistochemistry, the mass was diagnosed as an adenocarcinoma.