Part I: Benign Neoplasms and Lesions
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MAY 31, 2022
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I. Pseudo-neoplastic or benign (non-cancerous) growths
1.1 Xanthomas
Xanthomas are friable, yellow-colored, fatty masses that may be located anywhere on the body. “These are masses of foamy macrophages (cells that are part of the immune system), multinucleated giant cells (fused epithelioid cells), and cholesterol clefts that produce thickened, dimpled skin with yellow-to-orange coloration and occur infrequently in internal organs. They are not true neoplasms (tumors), but they are invasive, spreading into nearby tissue.” 17, 30
Xanthomas are caused by:
- High-fat and high-cholesterol build-up in the arteries and skin
- Lack of exercise
- Usually a poor, seed-based diet
- Poor husbandry, and
- Insufficient vitamin A30.
Lesions may be pruritic (inflamed and pus-forming) and are often associated with other pathology, such as lipomas, hernias, and sites of chronic irritation.8 Quaker parrots, macaws, budgerigars, cockatoos, cockatiels, doves, eclectus parrots, pionus, African grey parrots, Amazon parrots, and gallinaceous birds (chickens and other fowl) are prone to developing them, although they can be found in any psittacine species. Female budgerigars and cockatiels present with them most frequently.9,14,30 The average age birds tend to develop them is 10 years, although they can appear at any age.9,14,30
Image 1. Xanthoma on the underside of the wing of a cockatiel (image courtesy J. Miesle).22
1.1.1 Areas commonly affected
Xanthomas are usually found on the wing, sterno-pubic area (lower abdominal), and the keel.17 They are most commonly found over the ventral abdomen, thighs, hips, wings, eyelids, and around the face. They are rarely described within internal organs;8 however, there may be cholesterol buildup around the heart, specifically the aortic arch (Bob Dahlhausen, personal communication). Xanthomas may be diffuse (spread out) or discrete (forming individual lumps).29 The wings of most birds and the eyelids of Amazons are the most common locations for xanthomas. Diagnosis is generally by observation. The appearance of these lesions is quite unique. Fine-needle biopsy may also be used if the practitioner is uncertain.8,22,29
1.1.2 Treatment of xanthomatosis
Xanthomas are highly vascular (filled with blood vessels), and surgical excision, if necessary, should be undertaken with great care due to the risk of bleeding. Cryotherapy is sometimes used, but excessive bleeding can result from that as well.17,18 Therapy usually includes surgical resection, although with diffuse tissue involvement there may be an insufficient amount of normal skin to close the wound. A guarded prognosis is given for xanthomas covering large areas or having indistinct borders.8 The change to a low-fat, no-cholesterol diet, the addition of Vitamin A supplementation, and increased exercise may cause them to diminish or even disappear if they are small; however, if they are very large, this will not help.14 In that case, they need to be removed surgically. With smaller growths, surgical resection may be an option, but since they are highly vascular, attention to hemostasis (control of bleeding) must be observed. Xanthomas that cover the entire wing may require amputation of the wing.14 Drury Reavill, a pathologist, states that “The majority of xanthomas in our database that were surgically removed did not recur.” 8, 29 Failure to resolve xanthomatosis will lead to bleeding in the area, internal bleeding, and death.22
A proven, non-surgical method of treatment: A massage therapy technique for reduction and/or resolution of lipomas, fibromas, and xanthomas has been developed by J. Miesle. Early intervention with this protocol will resolve xanthomatosis. It will take time, but smaller xanthomas have been resolved using this technique, thus avoiding surgery and amputation. See the References for sources of the paper: Resolution of Xanthomatosis Without Surgical Intervention.22
Image 2. A pedunculated (hanging from a stalk) xanthoma. This lesion is quite advanced and will require surgical removal. Hematomas have formed; it has been bleeding, and the bird will not survive very long without having it resected (image courtesy Yariana Rubio Galban; used with permission).
1.2 Lipomas
Lipomas are benign, soft, yellowish, encapsulated masses composed of mature fat cells. They are most often located on the keel, abdomen, inner thighs, around the crop, or in the sterno-pubic area but can appear anywhere on the body.6,14 “These lobulated masses form in the subcutis (deeper part of the dermis) and, if traumatized, may become inflamed and necrotic (black from cell death).” 9 They are rarely seen on the back or the wings, but occasionally they may be seen around the cloaca. The masses are firm and movable and embedded in subcutaneous (under the skin) fat with the overlying skin, usually yellow in color.6 Lipomas are most often found in Amazon parrots, budgerigars, Quaker parrots, rose-breasted and sulfur-crested cockatoos, galahs, and cockatiels,6,8 and they rarely infiltrate into muscles or organs.6 Although these are benign tumors, they may grow to be large enough to interfere with normal leg and body movement.6,8,36
It is possible that abnormal thyroid gland function leads to the development of multiple lipomas.8 Generally, though, lipomas are caused by high-fat diets which lead to obesity. In obese hens, sterno-pubic lipomas may be associated with abdominal hernias and complicated resection (cutting out of tissue).17 Obese birds can develop fat pads at locations typical for lipomas, so tumors must be differentiated from fat tissue. They will recur, especially if they are not completely removed.30
Image 3. Lipoma on the breast of a Quaker before surgical removal (image courtesy Julie Burge; used with permission).
Image 4. Lipoma on the breast of a Quaker after surgical removal (image courtesy Julie Burge; used with permission).
1.2.1 Diagnosis of lipomas
Diagnosis is based on appearance. Radiography can be used to differentiate them from hernias and xanthomas. Lipomas may be an indicator of underlying diseases such as cardiovascular disease, hepatic lipidosis (fatty liver disease), hypothyroidism, and diabetes mellitus.6
Image 5. Racing pigeon with mesentery (area of internal organs) lipoma post-surgery (image courtesy Melbourne Pet Vet; used with permission). https://www.melbournebirdvet.com/interesting-cases
Image 6. Ulcerated lipoma in the inguinal area (insides of the thighs by the body) of a Galah (image courtesy Bob Doneley; used with permission) 6.
1.2.2 Treatment of lipomas
Therapy includes caloric reduction, diet change, and surgical removal when there is rapid tumor growth. Due to increased vascularity and bleeding of the overlying skin, the surgeon must be extremely careful when removing the lipoma. The bird may pick at the skin covering the lipoma, causing it to become ulcerated due to lack of blood supply.8 The environment should be changed to prevent trauma to the area.18 Sometimes a hematoma will form (a hematoma is a mass of clotted blood that forms in a tissue, organ, or body space as a result of a broken blood vessel; Merriam-Webster Dictionary). The usual cause of this is traumatic injury.
Images 7-10 Fibrous hematoma tumor removal (image courtesy Currumbin Valley Vet; used with permission). https://www.facebook.com/Currumbin-Valley-Birds-Reptiles-Exotics-Vet-141797059204766/
Image 11. Benign lipoma near a cockatiel vent (image courtesy Ann Pearn; used with permission).
Image 12. Benign lipoma on Amazon face (image courtesy Kim Proffit; used with permission).
Image 13. This bird was obese and living on seeds. The lipoma filled the body cavity (images courtesy Sofia Sangushko; used with permission).
Image 14. The radiograph of the lipoma in Image 13 (image courtesy Sofia Sangushko; used with permission).
A sedentary lifestyle and all-seed diets predispose birds to xanthomas and lipomas. Surgical intervention should wait until medical and lifestyle changes are tried. Doneley prefers to excise them only if the bird’s lifestyle is impacted; that is, if the bird’s normal range of leg motion is affected. If the lipoma is not ulcerating, these lifestyle changes often shrink it to the size that it is no longer affecting the bird’s quality of life. The weight should be monitored regularly. Then, if surgery is required, it is less stressful and painful for the bird, and post-surgical complications are kept to a minimum.6
1.3 Myelolipomas
“Myelolipomas are well delineated, benign neoplasms composed of fat and hematopoietic (blood-producing) cells. They are highly vascular, so attention to hemostasis during surgery is important as they can hemorrhage. They appear as masses of fat and resemble lipomas, xanthomas, and fibrosarcomas.”29 These are normal tissues that are located in abnormal places, and they may contain areas of mineralization or bone formation. As with lipomas, myelolipomas grow slowly and progressively. If the single masses are surgically removed, they are usually cured.30
Image 15. Myelolipoma on the liver. Diffuse enlargement of the liver with ill-defined, locally extensive white foci (image courtesy H. Hatai et al.; from: Hepatic Myelolipoma and Amyloidosis with Osseous Metaplasia in a Swan Goose (Anser cygnoides), Journal of Comparative Pathology, Volume 141, Issue 4, November 2009, Pages 260-264
https://www.sciencedirect.com/science/article/abs/pii/S0021997509000577 ).
Myelolipomas have been found on the wings, thighs, internal thorax, spleen, and liver. Affected species include adult cockatiels, lovebirds, parrotlets (Forpus species), budgerigars, Quaker parakeets, Amazon parrots, society finches (Lonchura domestica), a hyacinth macaw (Anodorhynchus hyacinthinus), and a saffron toucanet (Baillonius bailloni).”30
Treatment of myelolipomas
Surgical removal will cure the myelolipomas; however, the site may hemorrhage, causing a serious complication. They are usually found on adult and elderly birds. “They only become obvious and problematic if they become large or acquire secondary changes.” 29 These may cause the bird to have difficulty moving, or they may compress the tissues of nearby organs, creating functional changes.8
1.4 Papillomas
A papilloma is a benign skin tumor that can become malignant. It can occur on the skin and in the stomach lining.28 Unlike malignant tumors, papillomas are not caused by out-of-control cells but by a virus called Psittacid herpesvirus. Papillomas appear as wart-like lesions of the oral cavity and on the vent. Benign lesions sometimes do not require treatment as they disappear on their own; but if they continue to grow and start bleeding, they need to be surgically removed. They can be found on any species, but they are most often seen in Amazons, macaws, African greys, budgerigars, pigeons, and umbrella cockatoos.2, 6
Image 16: Internal papilloma disease (IPD) caused by a virus in a budgie (image courtesy Matt Gosbell, Melbourne Bird Vet; used with permission).
Image 17. Cloacal papillomas in an Amazon (image courtesy Gretchen Kaufman; used with permission).
“Papillomatosis is characterized by proliferative, grey-white growths on mucous membranes. In psittacines, there may be a link between papillomatosis and bile duct and pancreatic duct tumors. They are also found in the oropharynx, choanal slit, conjunctiva and eyelids, larynx, esophagus, crop, proventriculus, ventriculus, nasal mucosa, nasolacrimal duct, bile ducts, pancreatic ducts, and cloaca.” 30
Macaws, Amazon parrots, and hawk-headed parrots are the most commonly seen species that present with them. They will come and go over time. Signs include bleeding from the vent, lethargy, weight loss, cloacal prolapse, and agitation. Many birds show signs of anemia. Tests should be run to determine whether the lesion is a cloacal papilloma or a cloacal carcinoma which is infiltrative and typically has areas of necrosis and hemorrhage. Surgical removal of large masses may relieve some clinical signs.”30
Papillomas in African grey parrots
Some birds, often African grey parrots, develop cutaneous (skin) papillomas. These papillomas are wart-like lesions on the face, skin, and feet.30 Other locations are around the eyelid, commissure (junction of the beak and face), and legs. They are usually viral-induced in African greys, and internal papillomas (also most likely viral-induced) can become malignant, changing to squamous-cell carcinomas and melanomas. These may be found anywhere along the gastrointestinal tract.6,36 African grey parrots rarely develop lipomas, gastric carcinomas, fibrosarcomas, bile duct carcinomas, or xanthomas compared to other psittacine birds.8
A male adult Timneh African Grey presented with multiple cutaneous papillomas on the face. The lesions covered his head, affecting the eyes, upper and lower beaks, and skin. The bird was not treated, and after a year, the tumors became more widespread.8
Image 18. Small, benign skin tumor occurring at the commissure of the beak. It was easily removed (image courtesy Scott McDonald: Bad Beaks, A pictorial; used with permission; http://scottemcdonald.com/pdfs/Bad%20Beaks.pdf ).
Image 19. Hemangiolipoma on the tibiotarsus. Bone and muscle were not involved (image courtesy Julie Burge; used with permission).
Image 20. Hemangiolipoma on the tibiotarsus after removal (image courtesy Julie Burge; used with permission).
1.5 Granular-cell tumor
Granular-cell tumors are uncommon in avian species. They originate in embryonic tissue and are usually found on the skin of the head. The only reports are of an adult cockatiel and an adult Amazon parrot. Mycobacterial dermatitis is one possible cause of these masses. They are usually benign and cured by surgical removal.30
1.6 Hemangiomas
Hemangiomas are benign tumors formed by a collection of an excessive number of blood vessels. These benign tumors are seen more often than cancerous ones. This neoplasia may be internal or external and commonly appears as a red-purple, flat, firm lesion.17
Image 21. Hemangioma encompassing most of the area in the abdominal viscera (area containing the internal organs of the body) (from T. L Lightfoot; Overview of Tumors. Section I: Clinical Avian Neoplasia and Oncology in Clinical Avian Medicine 2006).
Image 22. Hemangioma in the conjunctiva on the eye of a cockatoo (image courtesy Bob Doneley; used with permission).6
They usually occur in the skin, feet, inguinal region, cloaca, side of the neck, wing, and spleen. Hemangiomas appear as circumscribed, soft, red-to-black swellings in the skin and subcutis. Complete surgical removal is curative for cutaneous hemangiomas.30
These are most often seen in budgerigars (Melopsittacus undulatus) and African grey parrots (Psittacus erithacus), but they are also reported in conures, Amazon parrots, cockatiels, Moluccan cockatoos, finches, ducks, Yellow-collared macaws (Ara auricollis), and doves.29
Image 23 Anesthetized budgie with capillary hemangioma below the left eye (image courtesy B. Coles)4.
“These tumors do not metastasize (spread throughout the body) but bleed profusely if traumatized and during surgery. They should be removed surgically and the harvested specimens sent for histopathology, no matter how small the lesion looks.” 4
1.7 Hemangiolipomas
An hemangiolipoma is a benign tumor made up of newly formed blood vessels clustered together with fatty tissue. In birds, they may be caused by the leucosis virus and are mainly sub-cutaneous (Saunders Veterinary Dictionary). Avian sarcoma leukosis virus (ASLV) is an endogenous (having an internal cause) retrovirus that infects the bird and can lead to cancer. These are fatty neoplasms that occur as solitary tumors of the skin and ovary in fowl. This tumor also occurs in the subcutaneous tissue of the body or limbs of adult budgerigars, the Yellow-collared macaw (Ara auricollis), cockatiels, lovebirds, blue-fronted Amazons (Amazona aestiva aestiva), and canaries. They are similar to myelolipomas.30
Hemangiomas appear grossly as circumscribed, soft, red-to-black swellings in the skin and subcutis. Although they can look similar to malignant melanomas, it is necessary that the clinician differentiates between the two. In Dr. Reavill’s cases, “Complete surgical removal resulted in survival times ranging from 2 months to 2 years without tumor regrowth.”29 “Metastases are rarely reported; however, this may mean they haven’t been sufficiently examined.”30
1.8 Fibromas and fibrosarcomas
“These tumors originate from fibrous connective tissue and are common neoplasms in birds. Cutaneous forms are more frequently found around the cere and beak, on the wings, and on the legs. Malignant fibrosarcomas appear more often than benign fibromas. Fibromas appear grossly as circumscribed, white-to-gray, raised or rounded, firm masses. The appearance of a fibrosarcoma may be similar, but lesions have more irregular and indistinct borders and are frequently ulcerated with the skin firmly attached to the mass.8 Fibrosarcomas are locally invasive, rarely metastasize, and have a moderate-to-high potential for recurrence, giving them a guarded prognosis. Other sites of reported tumor formation include the syrinx, liver, small intestine, cloaca, spleen, air sacs, and lungs. Therapy has included surgical removal, radiation treatment (in the past), and intratumoral cisplatin (chemotherapy, in the past).” 30
Image 24. Fibroma on the left wing carpal joint of the author’s cockatiel (image courtesy J. Miesle).
Image 25. A second fibroma on the right wing elbow joint (image courtesy of J. Miesle).
1.9 Cysts
1.9.1 Cystadenoma
“This is a histologically benign neoplasm derived from the glandular epithelium (skin glands) in which cystic accumulations of retained secretions are formed. In some instances, considerable portions of the neoplasm, or even the entire mass, may be cystic.” (Farlex Partner Medical Dictionary © Farlex 2012).
1.9.2 Feather cysts
Feather cysts are not neoplasms, but they do present a problem for the bird and owner. They are mostly found on the wing, usually on the last part of the wing, the carpus, but they can occur elsewhere on the body, such as the back. They can occur in any species but are most often found in canaries, parakeets, and cockatiels. Although most cysts are fluid-filled, feather cysts are usually dry and contain an undeveloped feather that has been trapped in the skin and is unable to emerge from the follicle. Some respond to opening and lifting out the feather, and some require removing the follicle. “They are not usually invasive but can become ulcerated. If they become problematic, they may be removed, which involves dissecting them from the surrounding tissue.” 3
Image 26. Benign cystic mass on a parakeet’s wing before removal. Removal was done under short anesthesia and healed well (image courtesy David Kersting, “Bird Medicine and Surgery;” used with permission).
Image 27. Rescued canary with multiple feather cysts. “It was in very bad condition and couldn’t stand or walk.” It passed shortly after the image was taken (image courtesy Julie Burge; used with permission).
1.10 Callouses
Image 28. “Benign cystic mass on a parakeet’s wing after we were able to remove the encapsulated mass (meaning it was all in a sac which we could separate from the wing)” (image courtesy David Kersting, “Bird Medicine and Surgery;” used with permission).
Image 29. A callous on the wing near the shoulder of the author's cockatiel (image courtesy J. Miesle).
This bony callous on the left wing was the result of an injury to the humerus. The bird already had a fractured manus and carpel bone from a previous injury when it was rescued. The callous grew and pushed on the small feathers that were growing under and around it. Those feathers continued to try to grow from under the callous and became damaged, disturbing the injury. The area was very painful for the bird when it was touched. Removal of the tiny, growing pin feathers gave the bird some relief until they grew back in again. Then the same problem recurred. The avian veterinarian would need to “pull the shafts and cauterize the germinal base to prevent the feathers from growing back.” The problem would then be resolved (R. Dahlhausen, personal communication). it was decided not to subject the bird to this procedure. This was not performed for this bird; it was in too poor of a condition to attempt the procedure. The bird passed away some time later.
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How to reference this publication (Harvard system)?
(2021) “Part I: Benign Neoplasms and Lesions”, Avian Health and Disease. Available at: https://www.ivis.org/library/avian-health-and-disease/part-i-benign-neoplasms-and-lesions (Accessed: 27 September 2023).
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