Avian neoplasias encountered in practice encompass most of the common locations and categories seen in other companion animals, with variations in distribution and morbidity.
Pseudoneoplastic Skin Conditions
Xanthomas are generally subcutaneous, yellow, fatty masses. The distal wing, keel, and the sternopubic area are common locations, although xanthomas may be found anywhere. Cockatiels and budgerigars are overrepresented, although xanthomas are seen in most psittacine species. The etiology is unknown; however, dietary improvement, including sufficient vitamin A or vitamin A precursors, has been curative in less advanced cases. Xanthomas tend to be very vascular. Surgical excision, if elected, should be undertaken with strict attention to hemostasis.
Lipomas occur most frequently in budgerigars but are rare in other psittacines. They are most often located on the keel or in the sternopubic area.
Cutaneous and Subcutaneous Neoplasia
Fibrosarcomas may be lobular, subcutaneous masses without skin involvement or may be seen as erythemic skin lesions. Fibrosarcomas tend to be locally invasive and recurrent. Surgical excision has been followed by both radiation and chemotherapy with some success.
Squamous cell carcinomas are most prevalent at mucocutaneous junctions of the head, on the distal wing, and on the phalanges. These tumors also tend to be locally invasive. In addition to surgical excision, radiation therapy has been attempted with some success, as has intralesional cisplatin. The uropygial (preen) gland may also develop squamous cell carcinoma.
Musculoskeletal neoplasms that have been reported in psittacines include osteosarcoma, chondroma, chondrosarcoma, hemangioma, and leiomyosarcoma. Wide surgical resection is the suggested treatment, although extrapolation from canine and feline oncology may suggest other methods.
Internal carcinomas include ovarian neoplasias (various cell origins), renal carcinomas, hepatic adenocarcinoma, and hepatobiliary adenocarcinoma (related to papillomas in Amazon parrots). Both carboplatin and cisplatin have been used successfully in various forms of internal carcinoma. Toxicity studies with cisplatin in cockatoos indicate that psittacine tolerance for this drug may be greater than that of mammals. Gastric carcinomas, generally diagnosed at necropsy, are often found at the proventricular-ventricular junction. Death from gastric neoplasia may be due to hemorrhage, gastric perforation and sepsis or endotoxic shock, or inanition and subsequent wasting.
Pituitary adenomas are most prevalent in budgerigars and cockatiels, but have been noted in the other psittacine species. These may be seen as acute neurologic conditions (eg, seizures, opisthotonos). Affected birds may also show signs related to the pituitary hormone(s) that are affected (eg, ACTH associated with polydipsia and polyuria).
Thymoma and thyroid adenocarcinoma have been reported in several psittacine species. Primary pancreatic neoplasias of variable cell origins have been reported.
Lymphoma may result in various clinical signs in pet birds, much as it does in other companion animals. Both chemotherapy and radiation therapy have been used successfully for treatment of lymphoma. No evidence of retroviral activity has been associated with psittacine lymphoma.
Primary respiratory neoplasia is uncommon in psittacines, except for a mixed pulmonary tumor reported in cockatiels. Metastatic pulmonary neoplasia may occur, but it is not noted with the same frequency as in dogs.
Most reports of chemotherapy in birds have demonstrated both higher tolerance for chemotherapeutic agents than expected, and less tumor response than desired. Anecdotal reports indicate that neoplasia in birds is more radioresistant than in mammals.
Last full review/revision July 2011 by Teresa L. Lightfoot, DVM, DABVP (Avian)