The other day in the oncology clinic at The Animal Medical Center, I saw a new patient and managed inadvertently to upset the owner. Her veterinarian diagnosed a “tumor” in her dog and when I asked her how long her pet had “cancer,” she burst into tears. To her, “tumor” implied a benign and curable disease, and “cancer” was a diagnosis that indicated something much worse.
I decided to look up the meanings of these words so I would not upset any new clients in the future as I discussed the conditions of their pets with them. For sources, I used the readily accessible websites, Wikipedia and Dictionary.com. I also got out my dusty copy of Dorland’s Medical Dictionary to be the ultimate source if there was question or conflict between the two websites.
A tumor is an abnormal growth of cells. The word tumor is derived from the Latin word meaning swelling. Neoplasm is another generic term which, like tumor, does not imply abnormality is benign or malignant. In essence, a lump is a tumor.
Tumors or neoplasms can be benign or malignant. Benign is typically defined by what it is not, rather than what it is. Benign tumors are not invasive and do not disseminate throughout the body (metastasize). Benign tumors typically carry a good prognosis for recovery. Adding the word malignant to the word tumor indicates a growth is invasive into the surrounding tissue or is expected to spread to various sites within the body. Common sites for metastasis are the lung and lymph nodes. Most typically think of malignant as being the modifier for tumor. Malignant may be used as a modifier for a non-cancer medical term meaning a very severe and potentially fatal form of a condition, such as malignant hyperthermia or malignant hypertension.
In all my sources, cancer was synonymous with malignant. Veterinary oncologists talk about three main types of malignancies in dogs and cats: sarcomas, carcinomas and hematopoietic tumors. The cutaneous mast cell tumor is a common canine example of a sarcoma. Like people, both cats and dogs can develop breast cancer, an example of a carcinoma. Lymphoma is the most common hematopoietic tumor in dogs and cats. In dogs, lymphoma occurs in the lymph nodes and in the cat, in the intestine.
Even though I am an oncologist by training, I never want any pet or person to have cancer. But now I will be clearer in my choice of vocabulary when discussing the nuances of tumors and cancer.
This may also be found in the “Tales from the Pet Clinic” blog on WebMD.com.
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