Part IV: Classification of Malignant Tumors in Birds
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MAY 31, 2022
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4.1 Hemangiosarcomas
This is a rare type of cancer that arises from the lining of the blood vessels. The tumor grows quickly and is highly invasive. The frequent cause of death is the rupturing of the tumor, causing the animal to bleed out. (https://en.wikipedia.org/wiki/Hemangiosarcoma).
An hemangiosarcoma is a malignant growth, also known as a malignant angiosarcoma. The beak, feet, and cloaca are the most common sites for these malignancies.30 They are also found in the spleen, heart, liver, skin, inguinal region, side of neck, myocardium, abdominal viscera, and on the long bones of the legs and wings.29
Image 43: Hemangiosarcomas on the liver (image courtesy Study Blue).
They have been reported in cockatiels, chickens, swans, Amazon parrots, lovebirds, African grey parrots, Pionus, budgerigars, parakeets, canaries, and finches. Hemangiosarcomas are locally invasive and multicentric (having two or more primary tumors). They appear inflamed and necrotic and tend to recur after they are surgically removed; most of them regrow within days to months.30
Etiologies for the development of tumors include long-term exposure to ultraviolet (UV) light and a genetic predisposition. Waterfowl may develop tumors in areas that are poorly feathered, suggesting an association with exposure to sunlight. An Amazon parrot, after long-term testosterone therapy for feather loss, developed a hepatic hemangiosarcoma.30 Complete surgical removal is curative for cutaneous hemangiosarcomas. Birds should be followed to check for metastases.29
4.2 Liposarcoma
Liposarcomas are malignant tumors of the lipocytes (fat cells) and are not commonly found in pet birds. They have been seen in budgerigars, cockatiels, an African grey parrot, a monk (Quaker) parakeet (Myiopsitta monachus), a macaw, and a green-cheeked conure (Pyrrhura molinae).7,14 Liposarcomas look similar to lipomas and are usually found near the keel bone or uropygial gland. They can invade nearby tissues and metastasize to other areas of the body.36
Image 44: Liposarcoma on the vent area of a budgie (image courtesy Johanna Nyden; used with permission).
Masses are yellow-to-grey, appear within the subcutis (the deeper part of the dermis), and are firmer, more infiltrative, and more vascular than lipomas. Cytologic testing may not differentiate between a liposarcoma and a lipoma, so a surgical biopsy is recommended for diagnosis. Liposarcomas spread locally, and several may occur in the same area.30 The tumor may be surgically excised, but these tumors often recur if the tumor is not completely removed.14
4.3 Squamous Cell Carcinoma (SCC)
Squamous cells are skin cells that form the surface of the skin and lining of hollow organs in the body such as in the respiratory and digestive tracts. Squamous cell carcinomas are malignant growths that are frequently seen in pet birds, and they are being found more frequently in the last few years.15 They are “comprised of moderately undifferentiated to poorly differentiated squamous cells.”14 These tumors are often caused by exposure to all forms of tobacco products and to high levels of sunlight or other sources of ultraviolet rays.15,33
Image 45. Squamous-cell carcinoma in a Sulphur-crested cockatoo at the uropygial gland; the pygostyle and uropygial gland were removed (image courtesy Melbournebirdvet.com; used with permission).
Image 46. Same bird as in previous photo after surgical removal of uropygial gland and pygostyle (image courtesy Melbournebirdvet.com; used with permission).
A survey taken of multiple institutions between 2012 and 2014 revealed 85 confirmed cases, mostly in cockatiels, amazon parrots, budgies, doves, cockatoos, conures, African grey parrots, Pionus, ring-necked parakeets (Psittacula krameri), lovebirds, elegant grass parakeets (Neophema elegans elegans), macaws, umbrella cockatoos (Cacatua alba), and small conures. Although many were treated with surgical excision or surgical excision in combination with radiation or chemotherapy, 71.7% (61/85) “showed progressive disease and died or were euthanized.”30,34 Squamous cell carcinomas have been diagnosed in chickens and other free-ranging birds.36
Image 47. Squamous-cell carcinoma on the beak of an African grey parrot (image credit Julie Burge; used with permission).
4.3.1 Areas of occurrence and recurrence
External squamous cell carcinomas usually involve the oropharyngeal (mouth and throat) area, tail base, wingtips, and axillary or side areas.15,28 They may occur anywhere on the body but are seen mostly in places where the mucosa transitions to skin, such as the eyes, mouth, nares, vent, and uropygial gland.17 They can be found in the oral cavity, esophagus, crop, proventriculus, infraorbital sinus, distal wing, and phalanges (toes).14,18,30 Cutaneous SCCs often appear as proliferative (spreading rapidly), irregular, broad-based masses, or wound-like ulcers. Tumors often develop at sites of chronic irritation and inflammation.14,30
They can appear similar to a keratoma (keratoacanthoma, a benign follicular tumor) or chronic ulcerative dermatitis and are associated with chronic feather-pulling and self-trauma.30 They appear in areas of chronic irritation, such as feather-picked areas, particularly under the wings.30 Cutaneous SCCs tend to be locally aggressive and recur, but there are few reports of metastases. Tumors are often associated with chronic, secondary bacterial and fungal infections.18 In one report, all of the birds with SCC affecting the beak, oral cavity, or esophagus either died or were euthanized due to uncontrolled tumor growth and secondary infections.30 Diagnosis is based on imaging (radiographs, CT scan) and fine-needle aspirate and cytology or biopsy of the lesion.18 “SCCs in the nasal sinuses and oral cavity have poorly defined borders and are associated with hemorrhage and necrosis of the surrounding tissues. They commonly are associated with chronic stomatitis (mouth inflammation), and caseous (cheese-like) material may be found within the mass. On examination, there is a thickening of the crop or esophageal wall with plaque-like masses.” 29 Most birds are on an all-seed diet, and Vitamin A deficiency contributes to tumor development.29 Birds with squamous cell carcinomas of the sinuses or oral cavity will display dyspnea (difficulty breathing), dysphagia (difficulty swallowing), anorexia (poor appetite), exophthalmos or exophthalmia (bulging eyes), and nasal discharge. Clinical signs of birds with SSCs of the crop or esophagus include anorexia, regurgitation, and depression.18
4.3.2 Treatment
Squamous-cell carcinomas tend to be extremely locally invasive, and complete excision is rarely accomplished, particularly in the oral cavity; however, if the mass is surgically resected and debulked, future treatment is more effective.17
Image 48: Squamous cell carcinoma on the neck of an Amazon (image courtesy Scott McDonald).
Image 49: Squamous cell carcinoma involving the mandible (lower beak), leading to overgrowth of the maxilla (upper beak). The end of the upper beak had punctured through the skin of the neck. The bird was euthanized (image courtesy Scott McDonald).
4.4 Fibrosarcomas
Fibrosarcomas are malignant tumors that arise from connective tissue.34 They are nodular, raised growths with a red surface on the skin.36 The masses are firm and have irregular and indistinct borders. Since they are invasive and have a moderate-to-high potential for recurrence, their prognosis is guarded.9 Fibrosarcomas are seen more frequently than fibromas.30 They may occur anywhere on the body but are most commonly found in the oral cavity and in the abdominal cavity.2 They may develop on the legs, face, beak, neck, sternum, syrinx (voice box), liver, small intestine, cloaca, spleen, air sacs, and lungs. On the bones, they appear as firm masses surrounding a long bone of the wings or legs with the skin firmly attached to the mass.8 Large fibrosarcomas might result in the skin over it becoming ulcerated from the bird picking at it or because the skin has become compromised.20,34 Fibrosarcomas are seen on the skin of the head in birds but are also seen in other locations such as in an area of chronic feather-pulling (self-trauma). The role of ultraviolet rays and carcinogenic agents is probably the same in birds and mammals, so areas of the body may develop cancers from that.20
Image 50. Ten-year-old Amazon with invasive fibrosarcoma on the soft tissues and bones of the head. Multiple masses were palpable throughout the body, and x-rays confirmed them (image courtesy J.M. Turrell in Harrison: Avian Medicine: Principles and Applications).
4.4.1 Subcutaneous fibrosarcomas
Some fibrosarcomas are subcutaneous (below the skin). These unusual lumps on the skin may have feathers jutting out in a strange way; these are covering the fibrosarcoma.17 Their cause is idiopathic (unknown); however, there are factors that contribute to their development:
- Poor diet, causing a lack of vital nutrients, which can lead to cancer formation.
- Exposure to toxic chemicals, causing a reaction in the bird’s body.
- Extreme, continuing stress, compromising the immune system.36
They can be found on any psittacine species, but are most frequently diagnosed in cockatoos, parrots, budgerigars, cockatiels, Quakers, lovebirds, and macaws.20,34
Image 51. Polycystic fibrosarcoma on a budgerigar (image courtesy Sofia Sangushko; used with permission).
4.4.2 Testing and treatment
Testing will include a find-needle aspiration or biopsy of the tissue, and diagnosis will be based on the test results. If it is a fibrosarcoma, treatment options should be discussed with the owner's veterinarian. These cancers can grow to a large mass and can spread to the internal organs. The bird’s quality of life, before and after treatment, will determine the method of treatment.36
If discovered early, surgical removal of the tumor or amputation of the limb can be curative; however, fibrosarcomas are likely to metastasize to the lung, liver, bone, or elsewhere with time. Birds with amputated wings or legs can continue with good quality of life; the birds will need time to recuperate and adjust to having only one wing or leg, but birds adjust quickly.20,33 Attention to the cleanliness of the wound and bandage is important; dressings must be kept clean and sterile. Good nutrition, rest, low-stress levels, and a quiet environment will aid in healing.36
Although they can metastasize, fibrosarcomas tend to be locally invasive and often recur with conservative surgical excision.17 The bird’s age is an important factor. If he is elderly, it might be kinder to allow him a quality of life in his remaining years. With cancer, there is no guaranteed cure yet.36
Image 52: Left: Lipoma and fibrosarcoma on a parakeet (image Phillip Sacks, Bird Vet Melbourne; used with permission). Right: Cutaneous fibrosarcoma at the commissure (junction of the beak and face) of the beak in a budgie. This is one of the more common malignant neoplasms diagnosed in pet birds. The subcutis of the wing, leg, commissure, neck, and sternum are regions commonly affected (image courtesy Scott McDonald).
Image 53: Fibrosarcoma of the beak in a parakeet. The beak and face are common sites for fibrosarcoma formation in pet birds (image courtesy MSD Vet Manual). https://www.msdvetmanual.com/exotic-and-laboratory-animals/pet-birds/neoplastic-diseases-of-pet-birds
Image 54: Fibroma and fibrosarcoma on the wing of a budgerigar (image courtesy Bob Doneley; used with permission).
Image 55: Fibrosarcoma on a budgerigar’s beak (image courtesy Bob Doneley; used with permission).6
Image 56: Fibrosarcoma on the wing of a parakeet (image courtesy of Louise Bauck; used with permission).
4.4.3 Fibrosarcoma Case Study
An 18-year-old sulfur-crested cockatoo was brought to Bird Vet Melbourne in 2005 with a lump at the elbow joint that extended toward the shoulder. It was firm and growing rapidly. A fine-needle aspirate showed that there was no infection, and X-rays determined the size and spread of the tumor. The wing was amputated at the shoulder; he was then unable to fly, but he recovered rapidly.32
Image 57: The growth can be seen as a large, circular mass just above the elbow and not extending to the shoulder. The tumor had invaded the bird’s muscle tissue. Fibrosarcomas frequently occur in older cockatoos. It would probably not have spread to other organs, but it could return to the original site (image courtesy Peter Sacks; Bird Vet Melbourne; used with permission).
4.5 Thymoma and Adenocarcinoma
Thymomas are localized neoplasms caused by dysfunction of the thymus gland.30 Although they are not often found in birds, thymomas and thyroid adenocarcinomas have been reported in several psittacine species and are usually located in the thorax or neck areas.17 “Because it involves the thymic tissue, it may be found anywhere in the subcutis of the neck between the thoracic inlet and the mandible.” 30 Thymomas have been reported in a lovebird, a budgerigar, a cockatiel, and two Java sparrows (Padda oryzivora). These tumors can contain cysts, and the enlarged mass is the only clinical sign. Although they don’t metastasize, they can often recur, and oral steroids have not been effective. These highly vascular tumors, when removed, will bleed profusely.30 Surgical excision is the primary treatment recommendation.17
Image 17. Cockatiel with feather loss around the uropygial gland. Cytology revealed multiple mitotic figures. The mass was removed and diagnosed as an adenocarcinoma (image courtesy Kenneth Latimer: Oncology. In: Avian Medicine: Principles and Application, Harrison, 1994).
4.6 Lymphoma and Lymphosarcoma
Lymphomas and lymphosarcomas are the most common lymphoid neoplasias in psittacine and passerine birds. Lymphomas are usually found in older pet birds, and Chronic Lymphocytic Leukemia (CLL) is rarely seen. “Multicentric lymphosarcoma involves two or more distinct primary tumors, usually in different quadrants of the tissue.”18 Lymphatic, hemopoietic (referring to blood cell production), hepatic, and cutaneous lymphomas are common.”18
Both pet and wild birds have been diagnosed with these growths. They can appear anywhere, but the liver and spleen are the two common locations in the abdominal cavity. Lymphomas have also been seen in the periorbital region.20 Malignant neoplasms are debilitating and cause chronic, untreatable anemias.3 Single lymphomas have been treated surgically.18
Image 59. Lymphosarcoma on a budgerigar’s back (image courtesy Sofia Sangushko; used with permission).
Image 60: “A four-year-old African grey was presented with a history of anorexia, weight loss, and depression. Supportive care was ineffective. The kidney and spleen were enlarged, and there were raised, white nodules in the liver at necropsy along with an accumulation of lymphoid cells in the nodules consistent with lymphosarcoma (white arrow) (image courtesy J.M. Turrel In: Oncology, Avian Medicine: Principles and Applications, p. 662, 1994).
4.6.1 Eye conditions associated with lymphosarcomas
Lymphosarcomas with eye conditions are seen more in Amazons and Congo African Greys than other species.17 There are numerous reports of exophthalmos in psittacines, particularly young African grey parrots. These have been diagnosed as retrobulbar (behind the eyeball) lymphomas. Cutaneous lymphomas often occur on the head or neck. Lesions are greyish yellow, diffuse or multifocal, and may resemble a xanthoma or inflammation. Clinical signs vary, depending on where the tumor is located.14
Image 61: Cutaneous lymphoma in the periorbital region in the eye (image courtesy D. Reavill). 29
4.6.2 Clinical signs associated with lymphosarcoma include:
- Periorbital or cutaneous swelling, blindness
- Depression, anorexia, weight loss, anemia
- Paresis (partial paralysis), lameness
- Abdominal swelling, diarrhea, scant droppings, regurgitation
- Dyspnea, polydipsia (excessive thirst)
- Feather loss, folliculitis (infected feather follicles).8
- Canaries usually present with abdominal enlargement, lack of singing, and dyspnea.29
4.6.3 Organs and tissues that are typically infiltrated by lymphosarcomas
- Gastrointestinal tract: liver, spleen, pancreas, mesentery (a fold of the peritoneum which attaches to the stomach), small intestine, pancreas
- Skin, bone, body fat, and periorbital muscles
- Kidneys, lungs, trachea, thyroid gland, thymus, oviduct, testes
- Sinuses, brain8
- “The liver is most frequently involved followed by involvement of the spleen and kidneys. These organs generally are enlarged and pale.” 29
African grey parrots are usually the species in which are seen periorbital masses, whereas Amazon parrots will develop choanal masses, and umbrella cockatoos will display multiple, nodular cutaneous growths. Lymphoid neoplasias have been reported in budgerigars, cockatiels, African grey parrots, mynah birds, cockatoos, Pionus, lovebirds, corellas (Cacatua sanguinea), parakeets, rosellas (Platycercus sp.), lorikeets, macaws, and an Amazon parrot. Lymphosarcomas have been reported in caiques (Pionites sp.), doves, and grey-cheeked parakeets (Brotogeris pyrrhopterus).29 The average age of diagnosis is 8 years.30
Aspiration cytology, biopsy, or bone marrow evaluation are used to diagnose the affected tissue. Treatment has been attempted but with little success.8
Image 62: Epitheliotropic (arising from skin cells) lymphosarcoma of the skin on the crown of the head of a budgerigar (image courtesy Bob Doneley; used with permission).
4.7 Cutaneous Pseudolymphoma
This tumor is composed of “large, nodular lymphocytic proliferations (many white blood cells that form small, round masses) that remain in the dermis.”30 It is mainly seen on the dermal face patches of macaws (Ara ararauna).30
4.8 Teratoma
A teratoma is a tumor composed of different kinds of tissue, none of which normally occurs together with or at the site of the tumor. It is a tumor of mixed content, such as bone, muscle, and feathers. Teratomas are most common in the ovaries or testes but can occur anywhere on or in the body. They have been found in the midline of the body, in a solid organ, and the urogenital tract. Some are benign, and some are malignant (Mosby's Medical Dictionary, 9th edition. © 2009, Elsevier).
Image 63: Cystic teratoma of the ovary.
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How to reference this publication (Harvard system)?
(2021) “Part IV: Classification of Malignant Tumors in Birds”, Avian Health and Disease. Available at: https://www.ivis.org/library/avian-health-and-disease/part-iv-classification-of-malignant-tumors-birds (Accessed: 29 September 2023).
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