Dog Skin Tumors: Identifying and Treating Growths on Dogs

While you are absent-mindedly petting your dog during the latest “Bachelor” episode, your hand feels something abnormal: a lump on or under the skin that wasn’t there before. Slightly alarmed, you part the hair and take a closer look. Your hands did not deceive you—there is a lump on your dog’s back! It’s squishy, and a little red. Is it cancer?

Many dog skin tumors found on dogs today are completely treatable with modern medicine, and many growths on dogs are benign and may require no treatment or minimal treatment.

When I see growths on dogs, I first advise the pet parents to not panic or feel afraid. Many dog skin tumors are benign, which means non-cancerous.

A lump on a dog’s back or a lump on a dog’s chest can be due to causes that aren’t classified as an emergency. The lump could be from sebaceous cysts, which are basically an inflamed sebaceous gland in the skin, not cancer, and easily treatable. Dogs can also get lipomas, which is a non-cancerous tumor of fat cells that can form soft, squishy lumps under the skin.

Insect bites and stings can cause the skin to swell and redden as well. Young dogs can get benign tumors called histocytomas and basal cell tumors that usually will spontaneously regress in a few weeks to a month. Dogs also get warts, moles, or other minor skin abnormalities that can result in a growth on their skin. All of these conditions are easily treatable and require a veterinarian’s attention.

If you notice a non-painful growth on your dog’s skin, relax and call your veterinarian to schedule an exam. If the growth is painful or rapidly growing, call your veterinarian’s emergency line, an emergency clinic or, at the very least, call your vet the very next morning. Emergency personnel should be able to advise you on whether your pet needs to be seen immediately, or if it can wait.

The last thing you want to do is panic—that will stress you out and it might stress your dog out as well.

After examination, your veterinarian may recommend testing the growth to see what it is. This involves inserting a small needle into the growth, removing some cells from the growth, putting them on a microscope slide and then examining that slide under the microscope.

This test will let your veterinarian look directly at the cells involved in the growth, and she may be able to determine what the growth is from the test. For example, if the growth is an abscess, then the test will show bacteria and white blood cells. If the growth has cancerous cells, your veterinarian will also be able to see those as well.

Sometimes, the cell type is unidentifiable, in which case your veterinarian may recommend sending the sample to the lab to have a pathologist take a look and give recommendations. Other times, your veterinarian may have a very clear indication of what she thinks the growth is and can give you treatment recommendations right away. My suggestion is that if she recommends having any dog tumors removed and submitted for testing, do it.

Sometimes pet owners are not clear as to why the tumor needs to be biopsied if we already know what it is, and the reason depends on the tumors behavior.

Some tumors are very naughty and send out tentacles of cancer cells into the surrounding healthy tissue that are not visible to the naked eye. If these cells are left behind, then the tumor will regrow from these cells.

The purpose of the biopsy is to make sure that all these cells are removed, or that the tumor is removed with “clean margins.” If the biopsy shows that cancer cells have been left behind or the sample has “dirty margins,” then a second surgery or radiation is required to eradicate all signs of cancer from that area.

Malignant, cancerous growths on dogs either invade healthy tissue locally or non-locally. Locally invasive tumors invade surrounding healthy tissues and tend to reoccur in the same location if they aren’t treated completely. Non-locally invasive tumors tend to metastasize, that is, invade the blood flow and travel other areas of the body. If your dog has been diagnosed with a tumor that tends to metastasize, then prepare yourself for a bigger diagnostic workup that includes imaging with X-rays or abdominal ultrasound and additional blood tests.

Sometimes dog tumors on the skin are indicative of a bigger problem under the hood, and in these cases surgical removal is not the recommended treatment.

Lymphoma in dogs is a very common cancer in dogs, and one of the first signs is a swollen lymph node either under the jaw, on the front of the shoulder, or on the back of one of the rear legs. Lymphoma is a cancer of the lymphatic system, and treatment consists of chemotherapy, not surgery.

If you notice a growth, talk with your veterinarian as soon as possible, and follow their recommendations.