Avian neoplasia (Proceedings)
Xanthomas are generally friable, yellow-colored fatty-appearing masses that may be located anywhere on the body, but are often seen on the distal wing, in the sterno-pubic area and on the keel. The origin of xanthomas is unknown, however, dietary improvement, including sufficient Vitamin A or Vitamin A precursors, has been noted to be curative in less advanced cases. Xanthomas tend to be very vascular and surgical excision, when necessary, should be undertaken with due attention to hemostasis. Diffuse xanthomas may be amenable to cryotherapy, but attention must be paid to maintenance of the vascular supply.
LipomasLipomas occur most frequently in budgerigars, but are also seen in Amazona spp, Ara spp., cockatiels (Nymphicus hollandicus) and other psittacines, and are often associated with excessive body fat. These masses are usually located on the keel or in the sterno-pubic area. Malignant liposarcomas are rare in psittacines.
In older psittacines, both xanthomas and lipomas may become life threatening when they are present in the sterno-pubic area. Concurrent abdominal herniation is often present, and when combined with an extensive mass, may result in difficulty in evacuation of the cloaca, abrasion, hemorrhage and infection. A combination of weight loss, altered environment to prevent trauma to the area, and surgery may be required. The practitioner must bear in mind that these older birds often have hepatic lipidosis, decreased hepatic function, coagulopathies and cardiovascular disease. Surgery, if necessary, should be as kept as non-invasive and as short duration as is possible.
If the bird is a good candidate for abdominal surgery, a gastrointestinal contrast study or ultrasound should be performed to determine if bowel loops are present in the herniated sterno-pubic area prior to surgical intervention.
Fibrosarcomas can occur anywhere on the body, but are most commonly seen on the face, in the oral cavity, associated with long bones, or in the abdominal cavity. They tend to be locally invasive and often recur with conservative surgical excision. Local treatment with radiation therapy is often indicated for providing long-term control. The metastatic rate is low, so local disease management is paramount. Surgical excision followed by both radiation and chemotherapy has been reported with some success. Strontium radiation therapy, although limited by depth of penetration, has been anecdotally reported as efficacious in several instances.
Squamous cell carcinomas
Squamous cell carcinomas (SCC) may also occur anywhere on the body, being most prevalent at mucocutaneous junctions, in the oral cavity, in the infraorbital sinus, on the distal wing, the phalanges, and the uropygial gland. Squamous cell carcinomas tend to be aggressively locally invasive, and complete excision is rarely accomplished. Radiation therapy has been attempted with some success, however squamous cell carcinoma appears to be an exceptionally radioresistant tumor and long-term control is rare. Anecdotal reports indicate that radio-resistance may be even greater in birds than in mammals. Strontium therapy when tumor depth is not a limiting factor has shown some promise in selected psittacine cases. Distant metastasis is rare, therefore systemic chemotherapy is not commonly utilized. Photodynamic therapy has been attempted in two reported cases. One case of SCC in the beak of a hornbill showed a positive result in decreasing tumor size but failure to eliminate the neoplasia. Other case reports had equivocal results. Intralesional cisplatin and intralesional cisplatin combined with cryosurgery have been effective in inducing partial remissions in three cases of oral and one case of submandibular SCC in psittacines in this author's practice. Species involved included a 26 year old Congo African Grey (Psittacus erithacus), an 8 year old male Eclectus sp. a greater than 30 year old Green wing macaw (Ara chloroptera) and a 36 year old Wagler's conure (Aratinga wagleri), (Maldonado, Lightfoot, Stevenson – unpublished data). Although to my knowledge, age-related data has not been collated, subjectively SCC does seem to occur with greater frequency in geriatric psittacines. The constant necrosis caused by the SCC itself and by the chemo and cryotherapies produce a fertile breeding ground for bacteria, yeast and fungus. Appropriate antimicrobial therapy should be continued throughout the duration of treatment to avoid septicemia.