Arnold Plotnick MS, DVM, ACVIM, ABVP
"“I’m feeling a lump in Annie’s abdomen”.
As a veterinarian, I’m sometimes forced to give unwelcome news. I could not have uttered words more devastating, however, than those just delivered to Christoph and Ellen Franzgrote. A year ago, they watched their cat Mia succumb to lymphosarcoma, a cancer of the lymphoid tissues. Mia couldn’t abide her chemotherapy and quickly surrendered to the disease at the age of five. Today’s routine wellness check on Mia’s daughter, Annie, yielded an abdominal mass.
The prevalence of feline cancer is increasing. Advances in veterinary medicine have allowed cats to live longer, and cancer is generally a disease of older animals. This is the fateful price cats must pay for living longer.
Cancer is unrestrained cell division and growth. Normally, cell division is tightly regulated. When a single cell undergoes a series of genetic mutations, cancer may arise, causing cell division to become unregulated, resulting in a tumor. While the cause of most cancers remains unknown, environmental agents can induce cancerous changes in cells, such as viruses, chemicals, radiation, and some hormones. The effects of these agents can accumulate over time, explaining why cancer more commonly affects older animals.
Another word for cancer is neoplasia (“new growth”), and tumors are sometimes referred to as neoplasms. Tumors are classified as benign or malignant. Benign tumors remain at their original site. Malignant tumors can invade surrounding tissues and gain access to the bloodstream or lymphatic vessels, and then be transported to nearby lymph nodes or other part(s) of the body. This is called metastasis, and is commonly how cancer spreads. The word cancer generally implies malignancy. While benign tumors are generally less worrisome and malignant tumors are more troubling, this distinction isn’t always clear-cut. A seemingly benign tumor may behave malignant clinically, impinging on nearby structures and becoming impossible to remove or treat.
Cats are susceptible to a variety of cancers. Among the most devastating are lymphosarcoma, squamous cell carcinoma, and mammary (breast) cancer.
Lymphosarcoma is a cancer arising from lymphoid tissues involving any organ. Affected cats ranges, on average, from 2 to 6 years, although any age cat is susceptible. Infection with the feline leukemia virus increases the risk of developing lymphosarcoma. This is especially true of younger cats. Older cats that develop lymphoma are less likely to be concurrently infected with the feline leukemia virus. Lymphosarcoma is often categorized by anatomic location. The five types are mediastinal (involving structures inside the chest), alimentary (digestive system), multicentric (the lymph nodes), leukemic (the bloodstream), and extranodal (other organs, such as the kidneys, eyes, nervous system, nasal cavity, and skin).
In cats, the most common sites are the gastrointestinal tract, the mediastinum (structures in the chest such as the thymus and associated lymph nodes), the liver, spleen, and kidneys. Fortunately, lymphosarcoma is fairly responsive to chemotherapy.
Squamous cell carcinoma (SCC) accounts for 15% of all feline skin tumors. These tumors usually involve light or unpigmented skin. Sun exposure increases the risk of developing SCC. Solar-induced SCC is referred to as “actinic” SCC. The most common locations are the hairless area of the nose, the eyelids, and ears. Older cats are at higher risk; the mean age for affected cats is 12 years. Siamese cats, with their pigmented skin, are less likely to develop SCC than other breeds. SCC of the skin is often amenable to treatment. Dr. Tim Rocha is a board-certified veterinary oncologist in New York City who has had good success treating SCC of the skin. “Except in advanced cases, we have several therapeutic options that all have good to excellent success rates. Surgery, radiation therapy, and intralesional chemotherapy (where the drug is injected directly into the tumor) have all been shown effective in treating this cancer”, says Dr. Rocha. SCC may also affect a cat’s mouth. This is often disastrous, as oral SCC is much worse than the skin form. “Unfortunately”, says Dr. Rocha. “95% of these oral SCC cases are diagnosed only after the cat shows dramatic changes in appearance, such as swelling of the jaw or face, severe weight loss, or blood in the mouth”.
Treatment for oral SCC is often unrewarding. “It is sad that we have yet to identify any treatments that are reliably helpful.” Surgery offers the best chance for survival, but most of the time it has progressed too far. “If a SCC is removed surgically in it’s entirety, a cat may become one of the rare 5% of cats that beat this diagnosis”, says Dr. Rocha.
Mammary tumors tend to develop in older cats. They account for 17% of neoplasms in female cats. Spaying dogs before their first heat lessens the risk of future mammary tumor development, and this also holds true for cats. Rarely, male cats will be affected. In cats, the behavior of mammary tumors is very different compared to dogs. While roughly half of canine mammary tumors are malignant, at least 80% of feline mammary tumors are malignant. Siamese cats have at least twice the risk of developing mammary tumors compared to other breeds, and they tend to be affected earlier, reaching a plateau at 9 years of age. More than half of affected cats show multiple gland involvement. Unfortunately, mammary cancer may spread to the lungs quickly, making the prognosis guarded or poor. Surgery is the best treatment option for feline mammary tumors. Dr. Kathy Kazmierski, a veterinary oncologist at Garden State Veterinary Specialists in New Jersey, says that the most important prognostic factor for survival is the size of the tumor at diagnosis and removal. “Tumors that are less than 2 centimeters big are much better than those that are 3 centimeters or greater”, she says. “Follow-up chemotherapy is often recommended”, says Dr. Kazmierski, “but there are not enough cases studied to know if that offers a true survival benefit”.
To make a definitive diagnosis of cancer, tests must be performed. Blood work, x-rays, and ultrasound provide a great deal of information, but ultimately, most cases require a biopsy to confirm the diagnosis."
MORE AT THE LINK ===> http://manhattancats.com/Articles/Feline_Cancer.html
No comments:
Post a Comment