Discovering a tumor on your favorite, furry friend can be unsettling. After all, no one likes to think of cancer—especially over someone they hold dear.

Although tumors are associated with cancer in dogs, it’s important to note that not all tumors are cancerous.

So what, exactly, causes these growths in dogs, and what can you do about it? Read on for the answers to your common questions about tumors in dogs.

What causes tumors in dogs?

There are several types of tumors that can affect your four-legged friend. Tumors can range in appearance from small bumps on a dog’s skin to large mass growths around the body.

In general, tumors are caused by an abnormal growth of the cells in the skin or tissue of your dog. But the root causes are often as diverse as the diagnoses themselves.

The following are the most common causes of tumors in dogs:

• Size: Overweight dogs are more prone to tumor growths.
• Diet: Though difficult to prove, carb-heavy diets tend to encourage growth.
• Sun exposure: Working dogs and others with fine or pale fur tend to develop melanoma and skin cancer, more than others.
• Breed: Some dog breeds are more prone to developing tumors than others, depending on the type of tumor.
• Environmental factors: Studies have found that environmental carcinogens range from chemicals used around the house—herbicides, paints, and solves—to those found in industrial areas.
• Hormonal abnormalities and genetics
• An imbalance in hormonal activity as a result of pregnancy or certain drugs
• Weak immune systems
• Age: With dog owners taking better care of their pets, dogs are living to the age where cancer is more common than in their younger years.

Are all tumors cancerous?

One of the greatest misconceptions of tumors is that they all lead to canine cancer. Often, the terms “tumor” and “cancer” are interchanged, which can be misleading. A tumor is not necessarily a cancer; the term “tumor” simply refers to a mass.

Tumors are either classified as benign or malignant. A benign tumor is non-malignant and non-cancerous. It is often localized, which means that it does not spread. Most benign tumors respond well to treatment. However, if left untreated, some benign tumors can grow large and lead to even more serious diseases.

A malignant tumor, on the other hand, is tied to cancer. Malignant tumors are cancerous growths which metastasize, meaning they spread to other parts of the body. These masses often resist treatment, and can even recur after removal.

What are the most common types of tumors in dogs?

• Mast Cell Tumors: Skin tumors which grow quickly and are usually very itchy. Unlike other tumors, mast cell tumors are less correlated with old age.
• Lipomas: Benign fatty tumors which are very common across breeds and don’t always require removal unless they affect a dog’s normal movement or activity.
• Osteosarcoma: Bone cancer that often affects a dog’s legs, found in larger breeds.
• Histiocytoma: benign tumors which develop through the immune system in dogs three years of age and younger. Referred to as “button” tumors because of their appearance as small, red, raised, and hairless bumps.
• Hemangiosarcoma: Cancer of blood vessels most often found on the spleen due to its larger blood supply. Hemangiosarcoma often requires surgery of the spleen, followed by chemotherapy.
• Melanoma: A form of cancer of the pigmented cells of skin in dogs. Tumors often appear as a black or dark brown. Many forms of melanoma are benign, but can metastasize, requiring a mix of surgery, radiation therapy, and immunotherapy.
• Lymphoma: A cancer of the lymph nodes, accompanied by lethargy, decreased appetite, and coughing in dogs.
• Papilloma: These benign tumors appear as cauliflower-like warts in dogs and are typically found in the mouth and around the eyes. Though benign, they can be painful and make chewing and swallowing difficult.

What do you do if your dog has a tumor?

Regardless of type, all tumors deserve to be examined by a veterinarian. Your veterinarian will be able to diagnose the type in order to prescribe the best course of treatment.

Cancer is the leading cause of death in dogs over 10 years old. However, there are several options of treatment available to you and yours today. From surgery, to chemotherapy, to immunotherapy and more, catching and treating a tumor as soon as possible is your best bet to creating the long, happy life your four-legged friend so deserves.