3.1. Subcutaneous and intracoelomic lipoma

This is one of the most frequently observed neoplasms in pet birds. Some studies suggest that this tumor has a 40% incidence in parakeets. Whether this observation is the result of genetic influence or just the popularity of pet parakeets is unclear. Other species commonly associated with this tumor are cockatoos and Amazon parrots. Obesity and advancing age probably play some role in this tumor as is the case in dogs and horses. Based on information gleaned from mammals, it is probably wise to not surgically remove a lipoma unless it has grown to a size to be uncomfortable to the bird.

3.2. Papillomatosis

This is common on the skin of the eyelids and junction of the beak and face. Parakeets, Amazon and African gray parrots are some of the species commonly affected. Canaries are affected to a lesser degree. Internal papillomatosis has a predilection for the cloaca and intestinal tract in some pet birds species (cloacal papilloma). As in mammals, these tumors are suspected to be caused by viruses, although none have been isolated. Recent evidence suggests that a herpes virus may be responsible for internal papillomas in pet birds.

Esophageal papillomas in a macaw

Cloacal papilloma in an Amazon

3.3. Cutaneous fibrosarcoma

This is one of the more common malignant neoplasms diagnosed in pet birds. The subcutis of the wing, leg, junction of the beak and face, neck and sternum are regions commonly affected. Species most often involved are: parakeets, cockatoos, parrots and macaws.

Fibrosarcoma at the commissure of the beak in a budgie

3.4. Squamous cell carcinoma

This is seen on the skin of the head in birds but is also seen in other locations. It is sometimes seen in a setting of chronic feather pulling (self trauma). The role of ultraviolet rays and carcinogenic agents is probably the same in birds and mammals.

Squamous cell carcinoma on the neck of an Amazon

3.5. Renal cell carcinoma

This is the most common kidney tumor in pet birds. In this instance also the budgerigar seems to be over-represented. The peculiar anatomic relationship of the kidney, lumbosacral plexus and spinal cord often result in a bird with this tumor clinically presenting with unilateral paresis or paralysis. Additionally, the prognosis for this tumor is poor because of the difficulty in performing surgery in this region.

3.6. Nephroblastoma

This is seen less frequently than renal cell carcinoma but seems to be more commonly associated with wild bird. In chickens this tumor is known to result from infection with certain strains of the avian oncornavirus.

3.7. Testicular teratomas

This is the most common testicular neoplasm seen in wild birds and poultry. In poultry it is most commonly observed in roosters over 3 years of age. Sertoli cell tumors and seminomas are commonly seen in parakeets.

3.8. Ovarian carcinoma

This is a common tumor in hens over the age of 4 years. The incidence of this tumor increases in proportion with age but is probably less common in pet birds because of the relatively low level of ovarian activity when compared with the hen. Ovarian tumors in birds spread by transcoelomic implantation or carcinomatosis rather than metastasis via blood or lymphatic vessels.

3.9. Hemolymphatic neoplasms

Although solid tumors are the chief, clinical manifestation of this form of neoplasia, when it occurs in the body cavity it may go clinically unrecognized for most of the disease course only becoming apparent in the final stages when the bird shows onset of lethargy and anorexia just before death. In this setting, the tumor can sometimes be diagnosed by the examination of peripheral blood smears when an agonal leukemia occurs.

3.10. Lymphosarcoma

This has been diagnosed in a number of pet and wild bird species with the tumors occurring in many different locations. The liver and spleen are the two common locations in the abdominal cavity but lymphomas have also been seen in the periorbital region. Although retroviruses are a likely etiologic candidate for this tumor, relatively little is known about the etiology of this tumor in comparison to the wealth of information on this form of neoplasia in chickens.

Cutaneous lymphoma

3.11. Erythrocytic and myelocytic neoplasia

Similar to that seen in chickens infected with the avian oncornavirus, this has been seen in pet bird species. The liver, spleen and bone marrow are the organs principally involved. Psittacine erythroblastosis is an apparently new disease that has be seen in wild New Zealand parakeets. The most distinctive clinical feature is progressive lethargy, sleeping posture, ruffled feathers and dyspnea. Some birds show a change in eye color with the iris becoming a light yellow instead of the usual orange red. These birds also have severe anemia. On autopsy there is prominent hepatosplenomegaly. Microscopically the bone marrow, hepatic sinusoids and splenic red pulp are packed with erythroblasts. No viral agent has been identified. The prognosis for this type of neoplasia in birds is uniformly grave.

4.1. Readings