What does cancer look like? Unfortunately, it is impossible to tell if a tumor is malignant or benign just by looking at it or palpating (feeling) it. The only sure way is to perform a biopsy, a technique whereby some cells are removed for microscopic examination. This can be done by a fine needle aspirate, in which a small needle is inserted into the mass and cells are extracted for staining and examination under the microscope. Sometimes, excisional biopsies are performed, in which all of the mass is surgically removed, then portions are examined microscopically. Another method is called an impression smear, which can also sometimes be used for attempting to diagnose malignancies. If the mass is ulcerated, a clean slide can be pressed into the mass for staining and examination.
Other tests can lead an avian veterinarian to a presumptive diagnosis. The history, or the owner’s interpretation of the progression of the mass, is very important. Thorough physical examination of the entire bird is very important, too. Radiographs (X-rays) can show classic lesions that give the appearance of a malignancy. Certain blood tests can also help in the diagnosis. But, the only way to know for certain if a mass is cancerous is to have a pathologist examine the suspicious tissue under the microscope.
How does a pathologist tell malignant cells from benign ones? Normal tissue cells usually appear uniform, with similar size and orderly organization. Cancer cells look less orderly. They often have haphazard organization and cells of varying size. Often, cancer cells are rapidly dividing (this is called mitosis), so counting the number of mitotic figures present during cell division helps the pathologist determine how aggressive the tumor is. The faster they grow and divide, the more dangerous the cancer is, as a general rule.
What kinds of cancers do pet birds get? Many types of tumors have been diagnosed in pet birds, including tumors of the skin and internal organs. Budgerigars seem to be one species of bird that is more prone to cancer than others. Probably the most common malignancy diagnosed is an internal tumor of either the kidney or gonad (ovary or testicle).
As the tumor grows, often the first sign of trouble is lameness of one leg. This occurs because the tumor often impinges on the nerves to the leg on that side, resulting in lameness. Eventually, the abdomen may become distended, either because the tumor continues growing or because fluid accumulates in the abdomen. Some tumors of the testicle or ovary produce hormones opposite of the sex of the bird, so a male budgie may develop a brown cere (the normal adult color of most male budgies is blue), or a female budgie that normally has a brown cere may suddenly develop a blue cere.
A male budgie patient of mine (with a beautiful, deep blue cere), named Fax, developed a testicular tumor that produced female hormones. His cere went from blue to tan in a short period of time. My client did not want to put him through a major surgery, and he went on to live for another year and a half with support care before succumbing to his cancer.
Ovarian carcinoma and adenocarcinoma are types of cancer that can be very dangerous, because surgical removal of the entire mass is difficult, if not impossible due to the ovary’s close associate with large blood vessels. For this reason, the cancer may reoccur after surgical removal. Clinical signs may include abdominal distension, fluid buildup in the abdomen, breathing problems, weakness or paralysis of the left leg and a visible or palpable mass in the abdomen.
Hens may also develop cancer of the oviduct. If caught in time, it might be possible to remove the oviduct with the malignancy, however, these tumors often metastasize to the surfaces of other internal organs. Just about the worst tumor that I have 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, unfortunately, the tumor was inoperable.
Tumors involving the kidney may cause signs of increased urination and concomitant (accompanied by) increased thirst and advanced tumors may result in gout.
Unfortunately, kidney and gonad tumors are often not detected until the mass has grown to a size that makes surgery risky. Some tumors will invade surrounding tissues and organs, making complete excision impossible and other tumors may have already traveled to other organs, called metastasis, which means that the bird will not be cured.