Part V: Cancers Specific to Body Systems and Organs

5.1 Cancer of the integument and feather follicles

5.1.1 Basal cell tumor (feather folliculoma)

Basal cell carcinoma is an epithelial tumor of the skin, and it arises from basal cells of the epidermis. They usually appear as “broad-based masses and have been found on the nictitating membrane (third eyelid) and in the cervical/ingluvial (neck and crop) region.” ³⁰  Recurrence is common after surgical removal. The canaries, specifically the Norwich and Gloucester, will often be seen with them since these species are ‘“bred for dense or unusual feather patterns. The lesions grow by the rapid production of new cells and produce firm lumps that contain yellow keratinaceous debris and resemble feather cysts.” ³⁰
 

In the past, basal-cell tumors (skin cancers) were not commonly seen in pet birds, but since the appearance of bird lamps, they are becoming more common. Birds that are exposed to the damaging ultraviolet rays of sunlight or bird lamps are being seen more frequently by avian veterinarians for skin cancer and cataracts.³⁶

5.1.2 Malignant melanoma

Although not often seen in birds, melanomas are one of the few tumors in which distant metastasis (cancer that spreads to other areas of the body) is possible.  Primary malignant melanomas have been diagnosed on the beak, in the liver, on the skin of the face, and in the oral cavity of psittacines and are commonly found in African greys.  Melanomas have been found to metastasize to the cardiac muscle, kidneys, and brain. Dr. Lightfoot reports that one African grey parrot was diagnosed with an “aggressive local invasion of malignant melanoma in the sinuses.¹⁸

"The lesions appear as brown-black masses with irregular borders that infiltrate into the surrounding tissues. These can look similar to cutaneous hemangiomas and hemangiosarcomas.”³⁰
 

One case report describes infraorbital swelling and a deformed maxillary (upper) beak in an adult, female African grey parrot. Numerous black masses were found in the nasal cavity, oropharynx, ovary, and pancreas. In another report, an adult male budgerigar developed a firm, dark mass in the left patagium (wing web) which was confirmed as malignant melanoma. Drury Reavill has seen two cases of malignant melanomas developing on the head in African grey parrots and one on the beak of a budgerigar. Other cases include an umbrella cockatoo with an isolated skin lesion, another with disseminated tumors (widely dispersed in a tissue, organ, or entire body), and a cockatiel with a wing tumor. All tumors recurred after surgical removal.³⁰ 

See Appendix D: Julie Hebert: Case Challenge: Feather destructive behavior in an African grey parrot. P. 103

5.2 Cancer of the Blood

Hematopoietic neoplasms

Hematopoietic neoplasms (developing in the blood) neoplasms arise from the high number of immature lymphocytes (white blood cells). They are often seen in domestic fowl but are rare in exotic birds.²⁷  

5.3 Cancer of the Musculoskeletal System

Tumors of the bones, muscles, and joints may be benign or malignant. Benign lesions such as chondromas, hemangiomas, and malignant tumors including osteosarcoma, chondrosarcoma, and leiomyosarcoma, have all been reported. They are usually treated by wide surgical resection or amputation. Complete excision of benign lesions is often curative, and debulking (decreasing the size of the malignant tumors) can be achieved with excision as well. If radiographs show bony lesions, a biopsy should be performed.¹⁸
 

Neoplasia of skeletal structures can be primary (osteomas, osteosarcomas, chondromas, chondrosarcomas, osteochondromas (bony projections or outgrowths on the surface of bones). Other structures are fibrosarcomas, hemangiomas or metastatic air-sac carcinomas, and other carcinomas. These tumors are recognized as firm swellings. It is important that they be distinguished from osteomyelitis. To differentiate between the two, “a deep-bone biopsy is required using a fine-needle aspirate or a bone-biopsy needle.” Amputation is the preferred treatment.⁶
 

5.3.1 Leiomyosarcoma

Leiomyosarcomas are malignant, vascular tumors of the soft tissues and smooth muscles. “These large, coelomic-cavity (internal area which contains the body organs) masses have been reported in the crop, alimentary tract, trachea, spleen, ovary, and oviduct.” ³⁰ Of all the psittacine species, only the budgerigars and lovebirds have been reported to have developed them since this type of tumor is rarely seen. In some cases, practitioners were unable to find the location of the primary tumor site due to extensive metastasis. It has only been diagnosed after death, and there has been no attempt to treat this tumor.³⁰

5.3.2 Rhabdomyosarcomas

Rhabdomyosarcomas (skeletal muscle tumors) are not common but do occur. Cancers originating from cartilage or bone (osteosarcomas) are presented from time to time.³⁶ These tumors are quite dangerous, and they usually originate in the long bones of the wing or leg, but they can also develop on the rib, skull, eye socket, toe, or tail bone. “This type of tumor may erode through the bone, resulting in a spontaneous fracture of the bone.” ³⁶
 

Rhabdomyosarcoma is a malignant tumor of the skeletal muscles that is occasionally observed in free-living and pet birds. A case of malignant rhabdomyosarcoma in the musculature of the right wing of a captive female cockatiel was investigated (Ober).

5.3.3 Chondromas and chondrosarcomas

A chondroma is a benign growth on the surface of a bone.¹⁷ It is composed of cartilage and can be found anywhere on the bird. A parakeet with a head tilt was found to have a chondroma of the skull. “The lesion was a pale yellow. It was a firm mass in the left cerebral hemisphere which had extended into the brain.”³⁰ Chondrosarcomas are malignant chondromas growing on the bone. This growth is treated mainly by the use of surgical excision.¹⁷
 

5.3.4 Osteoma and osteosarcoma

Osteomas are benign growths arising from the surface of bones.  An osteoma is composed of “dense accumulations of compact bone with ‘delicate intervening stroma’ (supporting framework of an organ made up of connective tissue fibers).” ³⁰ One peach-faced lovebird (Agapornis roseicollis) presented with a tumor mass that had arisen as a “bony proliferation of the skull. It was impinging on the freedom of movement of the jaw, impairing the bird’s ability to grasp with its beak.”³⁰ 
 

Osteosarcoma (OSA) refers to bone cancer, and the tumors are usually treated with amputation. There are very few references to this type of tumor in the literature; as a result, the species prone to it are not known.¹⁷ The neoplastic cells produce bone and tumor osteoid (material resembling bone). OSA’s occur in the long bones of the legs and wings. The suggested treatment is amputation of the limb containing the osteosarcoma.³⁶
 

One case is described in a 6-month-old female, blue-fronted Amazon (Amazona aestiva) that “presented with a swelling between the commissure of the mouth (where the top and bottom beaks meet) and medial canthus (where the tear duct is located) of the eye.”³⁰

Although this tumor was debulked surgically, it reoccurred a week later on the other side of the face. The large mass extended down to the jaw. It was again surgically debulked and treated with medication. Two years later, the tumor had not returned.³⁰
 

5.3.5 Osseous metaplasia

Osseous metaplasia is the formation of bone in soft tissue. With this, small pieces of mineralized bone are found in the lesions. These are rarely seen in birds.³⁰

5.3.6 Synovial cell sarcoma

This tumor is a rapidly growing mass that destroys joint and bone tissue and is rarely reported in birds. As of the writing of Dr. Reavill’s paper, no effective therapy had been found, and no prognosis was given,  although amputation was successful for one bird.³⁰

5.4 Cancers of the endocrine and glandular systems

5.4.1 Adrenal gland tumors

Carcinomas of the adrenal glands are not often seen in pet birds. A male budgerigar presented with anorexia, weight loss, dyspnea, abdominal distention, and ataxia (inability to maintain muscle control). A  large, 2-3 cm white mass near the kidney was found. “The carcinoma had infiltrated the testicle, anterior kidney, and air sac.”³⁰ In another case, an adrenal carcinoma was found in a scarlet macaw. His signs were polyuria (excessive urination), polydipsia (excessive thirst), weight loss, and decreased appetite. It had not metastasized. Other species in which adenomas were seen were a Quaker parrot and a conure.³⁰

5.4.2 Pituitary gland tumors

Pituitary adenomas are most prevalent in budgerigars and cockatiels, but they have been observed in other psittacine species. Signs include eye conditions, acute neurologic conditions, seizures, polydipsia, and polyuria.^14,18

Tumors reported in the pituitary gland are adenocarcinomas, carcinomas, and pituitary tumors, and these are most often seen in budgerigars under 30 months of age. Other signs include exophthalmia (bulging eyes) due to damage to the optic nerve, enlarged pituitary gland, tumor extension into the brain, cere-color changes (the cere is the featherless area that holds the nostrils), feather changes, opisthotonos (arched back, head back), vocalization, and blindness.³⁰

Tumors may also cause acute neurologic conditions (e.g., seizures, opisthotonos, ataxia, blindness, and difficulty flying). “Affected birds may also show signs related to the pituitary hormone(s) affected. Diagnostic tests are generally not useful. Diagnosis of pituitary tumors is based on the affected species and the clinical signs that the bird presents. The tumors are confirmed at necropsy (post-mortem examination).”¹⁴ 

5.4.3 Thyroid gland tumors

Carcinomas and adenomas have been found in the thyroid gland. This gland can also be involved as part of multicentric lymphosarcomas. Cockatiels and budgerigars are seen most often with it; Amazons present with it less frequently. The swollen gland causes clinical signs including regurgitation and changes in respiration; there may be a clicking or squeaking sound (thoracic click).³⁰ “Adenomas are usually smooth, red to purple, and may displace attached soft tissue, while carcinomas lead to distortion and enlargement of the thyroid gland.” ³⁰ There have been no reports of successful therapy. ³⁰

5.4.4 Uropygial gland tumors

The uropygial gland is a holocrine gland (holocrine glands are glands that secrete whole cells that have completely broken down for elimination from the body). It is located at the base of the tail. Its purpose is to condition and waterproof the feathers. It has antibacterial properties and produces a secretion called “sebum” which is odorless in most species.¹²
Sebum is composed of water-repellant waxes, lipids, and proteins, and in some birds, dead skin cells. It also contains the precursors for Vitamin D which, when exposed to UV light, convert to Vitamin D. As the bird preens, he spreads the sebum on his feathers and ingests some in the process.³
 

Some psittacine species do not have a uropygial gland,  including Amazon parrots, hyacinth macaws, and palm cockatoos. There is a high incidence of neoplasia, especially squamous cell carcinoma, associated with this gland.¹²
Malignant tumors of the uropygial gland are most often seen in the budgerigar and canary. The gland (which is normally bilobed, heart-shaped, and located at the base of the tail on the back) has a wick feather that the bird manipulates to pull the sebum from it; he then applies the secretion to the feathers.³⁶

SCC’s of the uropygial gland can occur and result in enlargement of the gland and ulceration.¹⁴ Tumors of the uropygial gland involve the abnormal swelling of the gland; it will sometimes present as an ulcerated mass with bleeding from the dorsal (upper) tail area. “Tumors must be distinguished from hypovitaminosis A with glandular metaplasia and hyperkeratosis, abscesses and impactions, and adenitis (inflammation of the gland). Taking a biopsy of the tissue will assist the clinician in diagnosing the growths.⁶
 

Tumors affecting the uropygial gland include carcinomas (most often squamous cell carcinoma or SCC), adenocarcinomas, and adenomas. These tumors often develop secondary bacterial infections. “Carcinomas are infiltrative and have poorly differentiated margins. Uropygial gland SCC’s produce glandular enlargement often coupled with tumor ulceration and self-trauma.” ³⁰ It is important to make sure these are true squamous cell carcinomas and not benign growths. In order to properly diagnose these tumors, bacterial and fungal cultures, cytology, and biopsies should be performed. Removal or debulking of the gland is the best treatment.³⁰ If the mass is small, it may be excised surgically; however, these masses are highly vascular and will bleed excessively. Most are not even found until they are very large.  Chemotherapy and radiation have been attempted but with little success.⁶  
 

These tumors can be benign adenomas or malignant adenocarcinomas and can adhere to the underlying bone. They must be differentiated from abscesses. Generally, they do not hemorrhage, but if the tumor has been allowed to become large, it may be difficult to repair. Removal of the gland does not usually have adverse effects, and the gland is not essential to the maintenance of the budgerigar's plumage since it is missing from several species of psittacines.³

5.5 Cancer of the Hemolymphatic System (tumors that spread from blood cells or lymph tissue)

Occasionally, tumors arising from the blood vessels may be found in the skin, liver, lung, spleen, muscle, mesentery, kidney, heart, oviduct, bone, or other tissues. These may occur singly or in groups. These are often very dangerous types of cancer, capable of invading locally or spreading to distant tissues, such as the lung, liver, or heart muscle.³⁶

Leukemia, lymphomas, and lymphosarcoma

Leukemia and lymphosarcoma affect the white blood cells and lymphatic system and are life-threatening to birds. Leukemia can involve either lymphocytes or granulocytes which are two cell lines of white blood cells. Leukemia is mainly seen in adult macaws. Lymphomas are cancers of the lymphatic system of the body involving immune cells. Aggressive chemotherapy has been used, but with little success; most birds will not go into remission. The viruses responsible for Marek’s disease and certain cancers in chickens are closely related, and researchers suspect  that some forms of leukemia in birds may be associated with some viruses as well.³⁶
 

5.6 Cancer of the Urinary tract

5.6.1 Renal tumors

The primary renal tumors of pet birds include embryonal nephromas (tumors of the kidney cortex—the outer portion of the kidney), adenocarcinomas, carcinomas, and adenomas. Most are seen in young to middle-aged, male budgerigars. Gonadal tumors also present with lameness, although less frequently than renal tumors.⁸
 

Budgerigars are prone to developing renal tumors. Common clinical signs are weight loss, vomiting or regurgitation, and unilateral lameness.⁸ Other signs include fluffed feathers, weakness, lethargy, anorexia, polyuria, polydipsia, dehydration, and gout (articular and/or visceral). In acute cases, uric acid deposits may be seen forming subcutaneously.⁶ Budgerigars and parakeets are extremely prone to cancer, and renal cancers are one of the more common forms. Birds that do not use one of their legs may be paralyzed in that leg due to a renal tumor pressing on the sciatic nerve. There is no suggested treatment. Their small size precludes any surgical option as these tumors tend to be invasive (image courtesy Olathe Animal Hospital; used with permission; http://olatheanimalhospital.com/762/renal-tumor-in-a-budgie/).²⁶
 

 “Metastases are rare, although they have been reported in the liver, oviduct, lung, and subcutis (the deeper part of the dermis) over the humerus. The coelomic cavity enlarges, and the ventriculus is displaced ventrally against the body wall. Renal adenocarcinomas and carcinomas appear as irregular, nodular, red-brown, or grey, occasionally cystic masses that can fill most of the coelomic cavity.  Adenomas seldom result in gross lesions. Treatment is by surgical removal, although there is a high mortality rate".³⁰ Tumors involving the kidney may cause signs of polyuria and polydipsia. Advanced tumors may result in gout formation.³⁶
 

The paresis (partial paralysis) is believed to be due to pressure on the lumbar plexus (nerves of the lower spine).⁸ Progressive, one-sided paresis occurs due to pressure exerted on the sciatic nerve by a renal tumor (carcinoma, adenocarcinoma, nephroma). “The hip joint may move normally, but there is a decrease in the bird’s ability to flex and extend,  and there is a lowering of sensation below the knee. Chemotherapy has been attempted, but with limited success. Prognosis is poor because of the difficulty in performing surgery in this region.”⁶
 

Gonadal tumors can also present with lameness, but not as frequently as renal tumors. The tumors are found in the top part of the kidney, and they grow by expansion and infiltration. Radiographically, there can be abdominal enlargement, and the ventriculus will be displaced ventrally against the body wall. These tumors can be removed but not without difficulty and a high instance of mortality.  Methylprednisolone, a form of chemotherapy, has been used as a palliative therapy but with little success.⁸
 

“The above radiograph shows the renal tumor pressing on the sciatic nerve, causing the leg on that side to be paralyzed.”²⁶ Any time a bird displays one-sided leg paralysis, it should be examined for a renal tumor. In this case, the six-year-old bird was diagnosed, using x-rays, with a renal adenocarcinoma. The owner allowed the bird to be treated with carboplatin, a chemotherapeutic drug. The bird showed some temporary improvement but passed away 3 months after starting treatment. Birds may live as long as a month with these tumors, but most owners opt for euthanasia since it can be a painful condition.”²⁶
 

5.6.2 Nephroblastoma (Embryonal Nephroma)

This is an unusual tumor, and it is generally large and unilateral. The affected kidney may contain multiple masses. They have been found in budgerigars, a 1-year-old pionus, and, in one case report, in a Moluccan cockatoo. The clinical findings are usually the same as those of a renal adenocarcinoma, and there is usually leg paresis.³⁰
 

5.7 Cancer of the reproductive tract

Testicular and ovarian carcinoma and adenocarcinoma are dangerous forms of cancer. The masses are difficult or impossible to remove surgically since the ovary is very close to large blood vessels; as a result, cancer may recur after surgical removal. “Clinical signs include abdominal distension, ascites (fluid accumulation in the abdomen), difficulty breathing, weakness or paralysis of the left leg, and a visible or palpable mass in the abdomen.”³⁶

Testicular and ovarian cancers are hormonally induced tumors. They cause lameness of one leg as the tumor impinges on the nerves to the leg on that side. Eventually, abdominal distention results as the tumor grows and ascites develops. Ovarian or testicular tumors may produce hormones opposite of the sex of the bird, so a male budgie may develop a brown cere (rather than the normal blue of males), or a female budgie’s cere will turn from brown to blue.³⁶

These tumors are not usually found until they have grown too large to be removed and have invaded nearby tissues and organs. In some cases, surgical removal is curative. If metastasis to other areas of the body is suspected, tests such as radiographs, MRI’s or CT scans are performed. Amputations are usually performed when malignant tumors are found on a limb to prevent future reoccurrence. While this may seem like a drastic measure, birds adapt very well to the loss of a limb or partial amputation.³⁶

5.7.1 Male reproductive tract tumors

Tumors of the male reproductive tract are reported in many species. They include Sertoli-cell tumors (which are the most common), interstitial cell tumors, seminomas, lymphosarcomas, teratomas, leiomyosarcomas, and carcinomas of the ductus deferens and epididymis.⁶ “Seminomas are tumors of immature germ cells that rarely metastasize.³⁰
 

5.7.1.1 Sertoli-cell tumors

A Sertoli-cell tumor is a fairly common testicular tumor in birds. It is most frequently reported in budgerigars and cockatiels and is associated with hyperostosis (excessive growth of bony tissue) and high levels of estrogen that result in color changes to the cere from blue to brown and hypertrophy of the cere (brown tissue growth on the cere). In other birds (cockatiels, Amazon parrots, finches, chickens, pigeons, ducks, and quails), the most common clinical sign is abdominal distention and respiratory difficulty. Metastases are rarely reported.⁸

Clinical signs include chronic weight loss, abdominal distension, unilateral paresis of the leg (due to sciatic nerve compression), cere color change, and hypertrophy of the cere in budgerigars (from blue to brown).⁶ The clinical sign of unilateral lameness is similar to that of renal tumors.²⁵

In 2004, Drury Reavill published the results of a six-year study she had conducted on the reproductive tumors of male birds. Testicular tumors are most often found in budgerigars (Melopsittacus undulatus) and pigeons (Columba livia). Other species were represented as well. ²⁴ 

The following are her conclusions:

“Between 1998 and 2004, her pathology lab tested 54 cases of male reproductive-tract tumors. The most commonly represented were seminoma and Sertoli-cell tumors. The tumors examined and the percentage of those tumors among the cases consisted of:

• Seminoma:  Present in 21 (39%) of the birds. These are tumors of immature germ cells of the testis. The most common symptoms were lethargy, anorexia, and dyspnea. The average age at diagnosis was 9.2 years. 
• Sertoli-cell tumor: These tumors were present in 24 (44%) of the birds. These are tumors that arise from the Sertoli, or sustentacular, cells. (Sustentacular cells provide structural and nutritional support to the sperm.) Clinical signs include anorexia, dyspnea, and cardiac changes such as heart murmurs and slow heart rates. Two budgerigars had their cere color change from blue to brown, (brown hypertrophy of the cere.)  Sertoli-cell tumors produced high levels of male hormone precursors which are feminizing hormones. Two cockatiels of the seven submitted validated metastasis to the liver. The average age at diagnosis was 10.2 years.”²⁵

The remaining nine (17% of the tumors) consisted of interstitial cell tumors, lymphosarcomas, leiomyosarcomas, undifferentiated sarcomas, and a teratoma. Because teratomas are hidden within other tissues, they are difficult to identify.²⁵

“The testicles may appear cystic and can be confused with an immature ovary when viewed endoscopically. Orchidectomy (removal of testes) is recommended. Unless the tumor has metastasized, the prognosis is good.”⁶

Various treatment modalities have been tried, including surgical removal, chemotherapy, radiation therapy, and hormonal therapy with mixed results depending on the species afflicted. For larger species (over 200 grams), surgical removal seems to be the best overall treatment and is recommended by most Nemetz. This is a delicate surgery that requires good microsurgical equipment and skills.²⁵

(At the time of this report [2004], small species were given radiation therapy by Orthovoltage [ Dr. B. Speer] or Strontium-90 therapy in hopes that the birds would be cured. Now, however, chemotherapy and radiation therapies are no longer considered useful as most of the birds die.)
 

This is an adult male budgerigar with a Sertoli-cell tumor weighing 50 grams. It grew from the right testis. “The testis was enlarged and replaced by a firm, white mass.” ¹⁰ This large mass had displaced the abdominal organs as it expanded the right testis and partially infiltrated the left testis. These fibrous, vascular tumors are not often seen in birds. Other tumors include seminoma, interstitial-cell tumor, lymphoma (a cancer of the lymphatic system of the body involving immune cells), undifferentiated sarcoma, and teratoma.  Seminoma and Sertoli-cell tumors are the most common tumors found in caged psittacines. Budgerigars are most often seen with them.¹⁰

Successful treatment depends on early diagnosis as these tumors can enlarge and hinder the prognosis. Dr. Nemetz presented his research at the Association of Avian Veterinarians (AAV) convention in 2009. His treatment protocol has shown great response to many testicular tumors. He administered “high-dose Leuprolide Acetate (Lupron) injections at specified intervals and then monitored the neoplasia radiographically.” The longest survival time had been over 3 years in a budgerigar with total resolution of the neoplasia.²⁵

5.7.1.2 Brown hypertrophy of the Cere

The cere is the soft, featherless area on the maxilla (upper beak) which holds the nares (nostrils). Brown hypertrophy of the cere is a smooth layer of growth on the cere which is most often found in budgerigars/parakeets. It can be caused by malnutrition, especially hypovitaminosis A, but it usually a result of hormonal increases as birds age or estrogen increases as the female budgie approaches breeding season.⁶ The brown tissue is easily removed by applying a very warm compress to it for a time and peeling it off with the fingernail. If left to continue, it can interfere with breathing. Sertoli-cell tumors in male budgies may present as a blue cere which turns brown. Chronic illness in budgies may cause pallor of the cere. Some tumors respond to surgical removal.⁶

5.7.2 Female reproductive tract tumors

5.7.2.1 Ovarian growths and tumors

Oviductal cancer is common. There has been some success with early removal of the oviduct and malignancy, but metastasis to the surfaces of other internal organs is common. Dr. Wissman states that the worst tumor she had ever seen was one that “developed in the oviduct of a Hyacinth macaw that actually eroded through the body wall and bulged out in the area of the hip on the left side. By this time, the tumor was inoperable.”³⁶

These abnormalities include congenital atresia (absence of the ovary due to degeneration), retained right ovary, and congenital ovarian cysts. Birds have only the left ovary; the right is vestigial (meaning a small part of the ovary exists, but over the millennia, the organ has ceased to function). These congenital ovarian cysts are common in budgerigars and canaries.⁶

Tamoxifen blocks estrogen production and has been used for avian ovarian carcinoma. The anti-estrogenic activity was suggested, and side effects were minimal in one drug trial. Depo-Lupron, leuprolide acetate, and Deslorelin implants have been effective.¹⁷

Typical tumors in females include:

• Granulosa cell tumors
• Ovarian carcinomas
• Dysgerminomas (malignant germ-cell tumor, similar to seminomas)
• Arrhenoblastomas (usually benign, secrete the male sex hormone, testosterone)
• Teratomas
• Adenomas
• Adenocarcinomas
• Leiomyomas

Signs are abdominal distension and yolk-related peritonitis or salpingitis (inflammation of the oviduct). There may be egg retention and oviductal impaction. Initial diagnosis is by ultrasound and radiography, followed by endoscopy and surgical biopsy. Treatment includes removal of the ovary if possible (usually not).(Chemotherapy and radiation therapy had been used in the past, but no longer.) Affected birds usually are extreme egg-layers, on all-seed diets, and receive little-to-no vitamin and mineral supplementation. There may be infertility or neonatal mortality. Signs include weight loss, ruffled feathers, anorexia, and lethargy. Eggs may become soft-shelled or abnormally shaped.⁶
 

Species that tend to develop ovarian tumors include: 
 

• Cockatiels 
• Budgerigars 
• Amazon parrots 
• Parrotlets 
• Macaws
• Cockatoos 
• African grey parrots 
• Grey-cheeked parakeets 
• Blue-crowned hanging parrots
• Monk parakeets
• Rosellas
   

In Reavill’s study, the most common ovarian tumors were adenocarcinomas and adenomas. Adenocarcinomas have a very poor prognosis, but with advanced microsurgery, benign adenomas have a guarded prognosis if the entire tumor can be removed.²⁵

5.7.2.2 Ovarian cysts

These may be congenital or acquired, and they may result from tumors or oophoritis (inflammation or infection of the ovary). If the cyst is small, there may be no signs; but if it is large, it may cause abdominal enlargement and dyspnea as it compresses the air sacs. “The cyst may be aspirated endoscopically, or hormone therapy may be attempted to reduce the size.”⁶

5.8 Cancer of the Gastrointestinal (GI) Tract

In general, the tumor is not found until a necropsy is performed, but if a fecal occult (not visible without a microscope) blood test is done and is positive, the result may point to a cancer diagnosis. Common hematology changes are anemia and hypoproteinemia (not enough protein in the blood). Radiographs may show that there is fluid and gas in the intestinal tract as well as a mass lesion. “Contrast radiography may help delineate a thickening of the proventriculus, incomplete filling of the proventriculus and ventriculus, and an irregular distention. The therapeutic intervention has not been reported.”⁸

5.8.1 Gastric neoplasia

Gastric adenocarcinomas are seen in budgerigars, cockatiels, Amazon parrots, macaws, lovebirds, and lories. These tumors produce thickening and irregularity of the wall with variable amounts of hemorrhage and necrosis. Ulceration, perforation, metastasis to the pancreas and lungs, and extension to adjacent organs may occur. Reported clinical signs consist of weight loss; weakness; inability to perch; head tilt; dark, red-brown stools; yellow-orange stools with undigested whole seeds; beak overgrowth; and polyuria. The feces may test positive for occult blood, and anemia and hypoproteinemia are common hematologic changes. Plain radiographs may reveal a mass lesion as well as fluid and gas in the intestinal tract. Antemortem (before death) diagnosis is rare, and therapy attempts have not been reported.³⁰

Death from gastric neoplasia may be due to hemorrhage, gastric perforation, and sepsis, or endotoxic shock (septic shock due to release of endotoxins by gram-negative bacteria), or inanition (exhaustion due to lack of nourishment) and subsequent wasting.¹⁷

5.8.2 Cancer of the esophagus, proventriculus, and ventriculus

When gastric carcinomas occur, they are usually found in the esophagus and at the proventricular/ventricular junction.  Amazons and budgerigars are predisposed to this type of cancer.¹⁸

Cancer of the proventriculus occurs more frequently than cancer of the ventriculus. It is rare to find cancer of the intestines.³⁶
 

5.8.3 Cloacal carcinomas

Cloacal masses have been found, mostly in Amazon parrots.³⁶
 

5.8.4 Cancer of the liver and bile duct

“Biliary and pancreatic carcinomas are frequently diagnosed in Amazons, and to a lesser degree, macaws, in conjunction with internal papillomatosis.”¹⁸  Other liver tumors that have been reported include hepatocellular carcinoma, cholangiocarcinoma, lipoma, sarcoma, hemangioma/sarcoma, and adenocarcinoma.¹⁸  

Birds may develop cancerous lesions in the liver or bile duct, and these may present as single tumors or multiple masses in the liver tissue itself. Early-stage carcinoma of the liver is often difficult to diagnose, and by the time the tumor is large enough to be noticed (usually by abdominal swelling), it may be too late to save the bird. There may be fluid in the coelom, resulting from damage to the liver. Some of these tumors may be diagnosed by using radiographs, ultrasound, endoscopy, laparoscopy, or biopsy. If a tumor is restricted to one lobe of the liver, it may be possible to excise that portion of the liver; however, these tumors may spread to the lungs, so it is always important to confirm that the lung fields look clear prior to attempting surgical removal of a solitary liver tumor. ³⁶ Tumors that metastasize to the liver are uncommon but include lymphoma and pancreatic carcinoma.¹⁸
 

In May of 2018, “A 20-year-old hyacinth macaw was presented for respiratory distress. The initial radiographs show enlargement of the heart, fluids in the coelomic cavity and air sacs, and enlargement of the liver/proventriculus area. The upper gastrointestinal (UGI) study shows the liver to be grossly enlarged, displacing the gastrointestinal tract. The patient did not survive, and the necropsy revealed liver cancer, pericardial effusion (fluid around the heart), and severe air sacculitis” (image and text courtesy Bart Huber; used with permission).
 

5.8.5 Cancer of the pancreas

Pancreatic adenomas, adenocarcinomas, and carcinomas have been found in the pancreas of pet bird species. These include mynah, toucan, cockatiels, a green-winged macaw (Ara chloroptera), and a yellow-naped Amazon parrot. “The clinical signs consist of polyphagia (extreme hunger);  anorexia; weight loss; abdominal distention; and voluminous, foul-smelling, light tan droppings. The pancreas appears either diffusely enlarged or as a firm, pale or white, nodular-to-cystic mass lesion. With adenocarcinoma and other carcinomas, there is the potential for liver metastasis or implants throughout the coelom. Surgical excision has been attempted in a few cases with survival ranging from 3 to 66 days.” ³⁰
 

Rhabdomyosarcomas are malignant tumors that originate from rhabdomyoblasts;  these tumors are rarely reported in domestic animals or birds (in free-living and pet birds). A paper by Maluenda et al., presented a case of rhabdomyosarcoma in a free-ranging yellow-headed caracara (Milvago chimachima).  The tumor originated from the muscle region of the proximal left humerus with metastases appearing in the left pectoral muscles, heart, lungs, and proventriculus (image courtesy J.M. Turrel,  Diagnosis and Treatment of Tumors of Companion Birds II, AAV Today, Vol. 1, No. 4 (Fall, 1987), pp. 159-165, Published By: Association of Avian Veterinarians, https://doi.org/10.2307/27670279, https://www.jstor.org/stable/27670279).

Cystadenocarcinoma

This form of a pancreatic tumor evolves from a mucus cystadenoma. With it, there is epigastric pain (pain that is felt in the middle of the upper abdomen) which can be mild or severe. It may spread from or to another part of the body. There is a palpable abdominal mass that may also be seen by ultrasonography or a computed tomographic (CT) scan. It is treated by surgical removal of the tumor or total pancreatectomy (Mosby's Medical Dictionary, 9th edition. © 2009, Elsevier). It is an adenocarcinoma with extensive cyst formation. (Saunders Comprehensive Veterinary Dictionary, 3rd ed. © 2007 Elsevier, Inc.)
 

Cholangiocarcinoma, or bile-duct carcinoma

Pancreatic adenocarcinoma (cancer of the pancreas) and cholangiosarcoma (cancer of the bile duct) may occur in birds with internal papillomatous disease associated with a herpes virus. ³⁶

“Bile duct carcinoma is an aggressive liver tumor that is locally invasive and will metastasize.” ³⁰ It’s possible that there is a connection between papillomatosis and bile duct carcinoma; however, this connection has not been confirmed. Amazon parrots appear prone to this carcinoma. In a study involving Amazon parrots between 4 months and 5 years, “Clinical signs include cloacal prolapse, weight loss, anorexia, acute trembling, coma, and seizures. All patients died within 6 weeks of presentation. Two of the six birds had concurrent cloacal papillomas, and one of these two also had a pancreatic ductal carcinoma.” ³⁰
 

A smaller number of macaws—and rarely budgerigars, cockatoos, conures, lovebirds, grey cheek parrots (Brotogeris pyrrhopterus), parrotlets, and Quaker parrots--have been reported with this carcinoma. The birds usually present with acute signs or are found dead. Necropsies reveal an enlarged liver with multiple white-to-tan, semi-firm nodules. Metastases are not ordinarily seen, but they have been reported in the lung and pancreas. Antemortem diagnosis is difficult to obtain, although there was one report of a confirmed diagnosis in a yellow-naped Amazon parrot (Amazona ochrocephala).³⁰ Chemotherapy has been attempted but with little success.⁸

5.9 Cancer of the Oral Cavity, Ears, and Eyes

5.9.1 Tumors of the eye

Retrobulbar (occurring behind the eyeball) neoplasms of the orbit and tumors of the nictitating membrane (transparent third eyelid in birds used for protection) have been reported.³
 

5.9.2 Tumors of the glottis in the oral cavity

The glottis is a slit-like opening into the larynx and trachea, lying on the floor of the mouth behind the tongue. Sometimes neoplasms and exudative lesions (sores that give off a fluid or puss) can affect this area, partially blocking the airways.³
 

5.9.3 Tumors of the beak

Tumors of the beak include fibrosarcomas, squamous cell carcinomas, liposarcomas, and keratoacanthomas (small, dome-shaped growths, usually benign). Some keratoacanthomas have been seen to transform into squamous cell carcinomas caused by exposure to the sun. They are composed of dead skin cells and keratin. Diagnosis is by biopsy. (Chemotherapy and radiation have been attempted with little success.) ⁶

Beak tumors can cause changes in the appearance of the beak. These include overgrowth, irregular peeling, cracking, necrosis, and irregular shortening or distortion. Tumors reported include carcinomas, sarcomas, malignant melanomas, and osteosarcomas. Budgerigars are prone to these growths. Most tumors cannot be addressed surgically, so the practitioner must differentiate them from granulomas or beak fractures. Squamous cell carcinomas often accompany chronic bacterial and fungal infections; dealing with these may prevent early definitive diagnosis.³⁰
 

5.10 Cancer of the Respiratory tract

Primary tumors of the lungs are not commonly found in psittacines, but tumors from other places often metastasize to the lungs. Fibrosarcoma, adenocarcinoma, hemangiosarcoma, malignant melanoma, mesothelioma, and osteosarcoma are types of tumors that may spread to the lungs.³³ Axillary (on the sides) cystadenocarcinomas are occasionally reported in psittacines, most often in cockatoos.¹⁸

Only a few species have been reported with primary lung tumors. Air sac adenocarcinomas in cockatoos, adenocarcinomas of the lung in ducks, and fibromas and fibrosarcomas of the lungs in chickens have been reported.⁹
 

5.10.1 Air sac carcinomas

Air sac carcinomas are rare tumors, and they may not be correctly identified as the primary tumor. They have been found in mature, large psittacines, mainly in cockatoos, African grey parrots, macaws, and Amazon parrots. The birds usually present with “cystic masses or bony lesions primarily involving the humerus. Cystic lesions were fluid-filled with large, friable (crusty and breakable), grey-brown masses. Radiographs of the humerus demonstrate deformed and proliferative new bone with areas of osteolysis (breakdown of bone). They can be diagnosed antemortem, but there is no effective therapy so far.” ³⁰
 

5.10.2 Nasal/sinus carcinoma or adenocarcinomas

“Carcinomas and adenocarcinomas of the upper respiratory system may arise from the nasal or sinus mucosa or from glandular epithelium.” ³⁰ Very large tumors may produce “distortion of the skull, and in severe cases, may impinge upon the brain.” ³⁰ These tumors appear grey-white, firm, and nodular. No therapy is available.³⁰ 
 

In Fig. 124, there is an image of an African grey with a growth on the head that had developed over a few weeks. It turned out to be squamous-cell metaplasia caused by hypovitaminosis A. This condition causes swellings around the lacrimal (tear) glands, respiratory sinuses, and salivary glands. In the oral cavity, it is characterized by caseous (cheese-like) white or yellow masses in the perilingual (tongue) region and around the choana (a slit at the top of the mouth). Improved diet, adding vitamins and minerals, and additional Vitamin A are needed.³

5.10.3 Pulmonary neoplasias in cockatiels

Cockatiels tend to develop a type of pulmonary malignancy that is invasive but does not metastasize well. These tumors were most probably carcinomas of pulmonary or thymic origin.⁹
 

Cockatiels are known for their tendency to develop neoplasia, especially tumors, of the skin and associated soft tissues. These are generally:

• Squamous-cell carcinomas 
• Fibrosarcomas, and 
• Myelolipomas,  benign, tumor-like lesions composed of fatty tissue and blood-producing (hematopoietic) elements.⁹

Some visceral (internal) tumors are also commonly seen in cockatiels. These include:

• Oviduct and ovarian adenocarcinomas 
• Seminomas (testicular tumors) 
• Sertoli-cell tumors, and 
• Pancreatic adenocarcinomas.⁹

“Pulmonary tumors in cockatiels are massive, discrete, infiltrative masses in the thorax (chest cavity).” ⁸  Affected birds are generally 1 to 10 years of age. The growths are usually found between the lungs, and the lesions “consist of large, firm, white-to-grey masses that replace areas of the lung. These tumors are very aggressive, and they may invade vertebrae or extend into the thoracic inlet, causing the collapse of the intra-clavicular air sac and compression of the trachea. Antemortem diagnosis is rare, and therapy has not been attempted.” ⁸