TUMORS IN PET BIRDS

INTRODUCTION

Tumors are firm tissue growths or swellings that may occur on the body (protruding from the skin), under the skin, or within the body. There are basically two types of tumors. Benign tumors, which do not spread, and malignant cancers, which spread and are usually termed as cancers in the medical world.

Birds kept as companion animals are increasingly living longer due to improved husbandry, nutrition, and veterinary care provided. As a consequence, a growing number of geriatric disease conditions, such as degenerative and neoplastic diseases, are diagnosed and managed by veterinarians.

Among companion birds, Psittaciformes are most frequently diagnosed with neoplasia, with budgerigars the most commonly affected species (17%–24% overall incidence) Passeriformes have the lowest reported incidence of neoplasia among companion birds. Cutaneous neoplasia, followed by urogenital neoplasia, is the most frequently diagnosed in companion birds.

DIAGNOSIS

As in any other species, a definitive diagnosis should always be obtained prior to determining the prognosis and treatment options. A body map, which documents the location and size of the neoplastic masses, should be performed anytime a new mass is found in a patient. Blood work should be performed to assess overall health as well as to look for abnormal blood counts, which could be linked to the presence of neoplasia.

An abnormal biochemistry profile may be the sign of organ involvement by the tumor or organ dysfunction related to age or other diseases and may preclude the use of certain therapies.

Many malignant tumors have the propensity to spread to other organs, commonly to lungs but also to coelomic organs or bones. For this reason, radiographs allow for visualization of bone lesions and soft tissue masses. However, CT images also allow for better surgical planning. Ultrasound is a valuable diagnostic tool in avian patients, in particular for large coelomic masses.

Cytology is a readily available tool, which is inexpensive and associated with low patient morbidity. However, a definitive diagnosis more readily is obtained by histopathology of a biopsy sample. Biopsy samples allow for evaluation of a larger specimen and provide information on architecture (important for staging) and surgical margins.

Additional immunohistochemical (IHC) testing may be necessary in some cases where cell morphology alone is insufficient to yield a definitive diagnosis.

TREATMENT

When possible, surgical excision of a tumor, with adequate margins, will always result in a better outcome. In fact, making every effort to obtain a presurgical diagnosis with cytology or histopathology as well as, if necessary, using imaging techniques to assess the extent of disease and help plan the optimal approach.

Radiation therapy is a form of local therapy. Several reports of radiation therapy in birds exist and show mixed results in terms of success and side effects.

When considering the use of chemotherapy in companion birds, several precautions must be taken. Every effort should be made to include a board-certified oncologist in the decision-making process. Dosages of chemotherapy are extrapolated from those used in canine and feline species; however, they may not be appropriate for use in avian patients.

In birds, cryotherapy has been used successfully after treatment with intralesional cisplatin in an African penguin (Spheniscus demersus) with choanal Squamous cell carcinoma.

The administration of long-acting synthetic gonadotropin-releasing hormone (GnRH) supra-agonists (eg, leuprolide acetate and deslorelin acetate) leads to a reduction of gonadal hormone secretion by overriding the physiologic pulsatile GnRH released from the hypothalamus. Sustained-release GnRH superagonists have been used in avian medicine to treat neoplasia of the reproductive tract in male and female birds.

COMMON TUMORS

Integumentary and Soft Tissue Tumors Squamous cell carcinomas are a malignant tumor of the epithelial cells lining certain tissues or organs. These can occur anywhere on the body and are commonly seen on the feathered skin, beak, uropygial gland, and phalanges and in the upper gastrointestinal tract (in particular affecting the crop).

LIPOMAS

Lipomas are benign neoplasms of adipose tissue and are the most common skin tumor in avian species. Lipomas are usually well circumscribed, but infiltrative lipomas have been reported in psittacines. Lipomas occur frequently in obese birds, specifically budgerigars, Quaker parrots, Amazon parrots, and macaws

Lipomas are most commonly found in the subcutaneous tissues and can arise anywhere on the body, including inside the thoracic or coelomic cavity. A recent study reported that lipomas were the most common neoplasm referred for a surgical procedure in birds.

FIBROSARCOMAS

Fibrosarcomas are a type of soft tissue sarcoma. They are most commonly seen in the facial/oral regions and bones and can be seen in cloaca the coelomic cavity. Fibrosarcomas tend to have a high recurrence rate after conservative surgery due to their invasive nature and the need for wide surgical margins.

MYXOSARCOMAS

Myxosarcomas are uncommon soft tissue sarcomas, mostly reported in chickens and in a kori bustard.

XANTHOMAS

Xanthomas are more common in the skin and subcutaneous tissues of gallinaceous birds and psittacines. Xanthomas are thought to develop secondary to obesity and hyperlipidemia with concurrent trauma. A diet supplemented in vitamin A or precursors may help treat these masses; however, no treatment is necessary unless the mass in causing functional problems or being traumatized.

MUSCULOSKELETAL TUMORS

Musculoskeletal tumors in birds are infrequently reported in the literature. The most common are osteosarcoma and chondrosarcoma. Surgery is the treatment of choice although behavior of this neoplasm and expected outcome are not described in birds.

HEMATOPOIETIC TUMORS

Lymphoma is one of the most common neoplasms in companion birds. Lymphoma can manifest in birds as a visceral, cutaneous, retrobulbar or periorbital, oral, or leukemic disease. Diagnosis is obtained via cytologic or histopathologic diagnosis. Treatment of systemic disease is performed with chemotherapy; local disease control can be achieved with surgery with or without radiation therapy.

RESPIRATORY TUMORS

Respiratory tumors in birds seem to be highly locally invasive and diffuse metastatic disease to intracavitary organs and bones is common.

GASTROINTESTINAL TUMORS

Adenocarcinomas of the proventriculus or ventriculus are described in birds, the most common site being the isthmus. Cholangiocarcinomas have most commonly been described in Amazon parrots.

UROGENITAL TUMORS

Ovarian and oviductal neoplasms of companion birds include adenocarcinoma, adenoma, carcinomas, cystadenocarcinomas, granulosa cell tumors, and hemangiosarcoma. Renal carcinomas are the most common renal neoplasms reported.

OCULAR TUMORS

Retrobulbar or orbital lymphoma is among the most common ocular neoplasms.

REFERENCES:

Zehnder, A., Graham, J., Reavill, D. R., & McLaughlin, A. (2016). Neoplastic diseases in avian species. Current therapy in avian medicine and surgery, 107-41.

Robat, C. S., Ammersbach, M., & Mans, C. (2017). Avian oncology: diseases, diagnostics, and therapeutics. Veterinary Clinics: Exotic Animal Practice, 20(1), 57-86.

URL: https://vcacanada.com/know-your-pet/tumors-in-birds