Canine Lumps and Bumps: Superficial Tumors on Dogs

Dr. Patty Khuly

Tumors on Dogs

Let me set the stage: You’re having dinner with your whole family when your youngest turns to you and shouts, “Maggie has a bump!” Next thing you know you’re making an appointment to see your veterinarian (hopefully).

While seldom an emergency, lumps and bumps on the surface of the skin, toes, ears, mouth, or anal area are among the most common reasons pet owners visit their veterinarian. Which only makes sense since they’re not supposed to be there!

Thankfully, not every lump, bump, protuberance, or tumor is cancer. Just because it’s ugly, raw, irregular, hairless, or even bleeding doesn’t mean it’s a big bad emergency that needs to come off right away. But that doesn’t mean it doesn’t need to be seen or treated, sometimes even with removal every bit as much as if it were a malignancy.

But first, a few terms:

Mass: A mass is a general term for any undiagnosed lumpy thing that clearly doesn’t belong to the normal anatomy (inside or out of the body). The word “growth” is similarly non-specific.

Tumor: Though often associated with something that’s really bad, like “mass,” “tumor” is also a general term. This word is interchangeably used with mass to mean any abnormal growth inside or outside of the body.

Cancer: This is a disease defined by the uncontrolled division of abnormal cells. It can lead to abnormal growths anywhere in the body but can also be found in the blood (like leukemia or lymphoma).

Benign: A mass that’s benign is non-cancerous. It’s also a general term for many non-cancerous disease processes that are non-harmful or not clinically problematic.

Malignant: A cancerous mass. It also specifically refers to some disease processes that are especially harmful.

Cyst: Typically a fluid-filled mass characterized by a well-defined lining of tissue. They can be small or grow impressively large.

Enough of that. On to the offenders! Here’s a list of the top f lumpy bumpy things we’re likely to see on our dogs’ skin:

Mast cell tumor: First up, a cancerous one. The mast cell tumor is the most common malignant tumor of the skin. It can look like almost anything on the surface of the skin but tends to show up as a partially hairless mass that may or may not be red or ulcerated. Luckily, these are considered curable via surgical excision in a great many cases.

Melanoma: Superficial melanomas are typically found in the mouth or toes of dogs. These can be especially aggressive malignant tumors, which is why any lump in the mouth or toenail bed needs to be seen by a veterinarian ASAP. Note: These tumors aren’t always black, contrary to what many people tend to believe.

Sebaceous cysts: These cysts arise from the sebaceous glands of dogs. They’re filled with gross fatty material and they’re sometimes easily expressed, pimple-like. Most don’t get bigger than the size of a pea and they can get to feeling quite firm over time as the material within starts to dry and harden. Strictly speaking, they don't need to come off, but infected sebaceous cysts can become quite the non-healing nuisance if they’re not surgically treated.

Papillomas: These wart-like masses look like small cauliflower-type growths on the surface of the skin. Some dogs are predisposed to them. They’re typically pinkish, gray, or black. They do not need to be removed but some owners want them gone anyway, for cosmetic reasons.

Lipomas: These are the most common skin tumors of dogs. They feel like soft, fleshy lumps that are typically hemispherical or round. The deeper ones can feel firmer and scarier, but they’re almost always benign too.

Skin tags: These benign masses look like tiny, often elongated outcroppings of skin. We see them a lot on the bellies, limbs, and chins of dogs, but they can be anywhere on the skin, really.

Squamous cell carcinoma: These red, ulcerated, irregular, angry-looking tumors typically arise in the mouth of dogs (technically they can be anywhere on the skin though). They’re considered aggressive cancers, but they can be treated surgically if they’re addressed early.

Any skin growth should be brought to the attention of your veterinarian. In the case of any tumor larger than a pea, veterinarians will typically insert a needle to extract some cells for microscopic analysis, called a fine needle aspirate. Other tumors may need to be biopsied more extensively, meaning that a surgical incision may be in order.

The good news is that most lumps and bumps on the skin are benign. But that doesn’t mean you shouldn’t pick up the phone and make an appointment as soon as you spot one.

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