If your dog or cat has been diagnosed with cancer, it can turn your world upside down. Many of my clients are suddenly thrown into a state of shock and panic. No matter your experience, you will be bombarded with various new terminology that can be confusing and stressful. To help you wade through all of these new words, I put together a list of commonly used terms that your veterinarian or veterinary oncologist might use.

What is cancer? While a normal cell grows, divides, and dies, a cancer cell is genetically altered so that it does not die. Cancer cells grow uncontrollably. All different types of cells in the body can become cancerous. Sometimes we know the cause for the cancer, and sometimes, the cause is unknown.

Cancer is classified as benign or malignant.

A benign tumor is one that does not have the potential to spread other parts of the body. Often these are small, do not need to be treated, and do not cause problems. However, some benign tumors can grow to very large sizes and thus may lead to problems that require treatment.

A malignant tumor is one that is locally invasive as well as having a risk of spreading to other parts of the body.

Metastasis is the process of a tumor spreading from one part of the body to another. So, when a cancer has spread, a doctor will often say the cancer has “metastasized.”

Tumor grade is determined from a biopsy sample. Generally, tumors are classified as low (I), intermediate (II) or high (III). The higher the grade, the more aggressive a tumor behavior is expected to be. Grade is based on what the cells look like under the microscope, how abnormal they look. The more well differentiated they are and the more normal they look , the lower the grade and the better the prognosis. A poorly differentiated tumor looks very abnormal and is more aggressive.

Staging of disease is done to look and see if the cancer has spread (metastasized) to other parts of the body. Stage helps to predict how aggressive a cancer is and will impact a patient’s prognosis. It helps a doctor figure out the best possible treatment options, follow up and support care. Categories of stage vary from one cancer type to another. The lowest stage means the cancer has not spread yet. The next stage often implies that the cancer has spread to the closest lymph node. As the cancer spreads to other lymph nodes and internal organ sites, the stage increases.

Phase 1: Tests that tell why type of cancer your dog or cat has

Fine needle aspirate (FNA) is a simple, minimally invasive tool to get a sample of cells from tissue. It is done using a syringe and small needle placed into abnormal tissue. Suction is often used to collect cells into the needle and syringe. The sample is then squirted on a glass slide for review under a microscope. This procedure can often be done in an awake patient.

Cytology is the examination of cells under the microscope from samples collected via fine needle aspiration. It can be used to obtain a diagnosis of cancer and to evaluate lymph nodes for metastasis. It is not as accurate as a biopsy, due to the limited sample size. It does not accurately determine tumor grade.

Biopsy is the process of collecting a wedge, core, or larger piece of tissue for diagnosis. This procedure is typically done under sedation with a local block or under general anesthesia. The sample is placed in formalin for preservation and then sent out to a lab for evaluation. There are two types of biopsy procedures: 1) incisional biopsy- a small piece of tumor is taken and submitted for evaluation, or 2) excisional biopsy- a surgeon takes the entire tumor (or as much as possible) and submits it for evaluation.

Histopathology is the examination of a biopsy specimen for diagnosis. It generally provides much more information than cytology and is used to determine whether a tumor is benign or malignant, tumor grade, and subtype. In addition, if an excisional biopsy is done, samples are evaluated to look at margins.

Stay tuned for additional vocabulary words in upcoming blog posts.