(First published May 2005 in The Mayor’s Alliance for Mayor’s Alliance for NYC’s Animals newsletter, Out of the Cage!)
While many of us may have previously equated cancer with death, there have been great advances in the treatment both of humans and animals with cancer. With increasing awareness, we are able to move away from unnecessary feelings of helplessness. Veterinarians today can offer far more options with regard to diagnosis and treatment, and more clients are willing to pursue those options. If you are concerned that your companion animal might have cancer, the following information might be helpful.
Cancer is a term that includes a broad group of diseases, each of which is managed differently. An oncologist is a doctor who specializes in treating cancer.
A tumor is simply a swelling. A wide number of lesions are classified as tumors. Many of these are completely curable. Benign tumors are generally harmless in the sense that they are unlikely to spread to another part of the body or recur in the same location. It is occasionally advisable to remove even a benign tumor if it is becoming irritated or infected. Some benign tumors, such as cysts or fatty deposits, can become so large that they become a physical hindrance to the animal. However, small, inactive, benign tumors frequently can be ignored.
Malignant tumors, on the other hand, have the potential to spread to other parts of the body, or recur in the same place after being removed. There are many “shades” of malignancy from one type of cancer to the next, or even within the same class of cancer. Mast cell tumors are good examples of the shades of malignancy. There is a huge variability in “danger potential,” from mild to life threatening. We use a fairly complicated system to help us calculate a prognosis and treatment plan for an individual tumor.
Grading a tumor is done by a pathologist by looking at a sample of the tumor under a microscope. Certain features which are known to contribute to the aggressive nature of a tumor are scored and added.
Staging a tumor involves determining the extent of distal spread at any given time, such as to a lymph node or distant organ.
There are numerous ways to obtain a sample for the pathologist. A fine needle aspirate is the least invasive, but will yield only a few cells on a slide. An incisional biopsy requires anesthesia, but allows us to remove a larger piece of the tumor for a more accurate diagnosis. An excisional biopsy allows us to remove the whole tumor. There are appropriate circumstances for each of these procedures.
When we remove a tumor, our goal is to achieve clean margins. (We don’t want to leave any tumor behind.) Some tumors are located in areas that prohibit complete surgical excisions. Some tumors appear to be completely excised macroscopically (to the naked eye), when in fact invisible cells are extending to the edges of the surgery site microscopically.
Treatments might include surgical excision, chemotherapy, radiation, or any combination of these, depending on the cancer. There are a whole host of traditional and newer adjunctive therapies available as well.
Your veterinarian can guide you through the appropriate diagnostic tests and help you decide on a treatment protocol that is right for you and your pet.