10 Types of Tumors in Dogs You Can See on the Skin Get to the Bottom of the Bumps on Your Dog's Skin

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Tumors can crop up in dogs of every breed and age. Many of these skin tumors end up being benign and nonthreatening. Here is a quick list of the most common types of skin tumors in dogs.

10 Nasty Dog Tumors Detectable on the Skin (Vet Approved)

While some tumors occur deep within the canine body and are impossible to detect visually, others can be discovered by pet owners during grooming, petting or via simple observation. Don’t be alarmed and start looking at scary dog skin cancer pictures on the internet every time you find a new lump or bump. In most cases, a small red bump on dog skin can turn out to be a simple skin abnormality or a tumor that’s either benign or easily treatable.

If you do detect a weird growth, it’s very important to visit the vet to learn about the cause and if it needs to be treated. Below are some tumors that you might find by visually inspecting or touching your dog’s skin.

1. Mammary-Gland Tumors

These tumors are rarely found in unspayed females. However, if your dog is not spayed, these tumors are fairly common. The tumor can be detected by touch, can be large or small in shape, and they are most often located in the glands closest to a dog’s groin. Larger tumors, measuring more than an inch and a half tend to have a worse prognosis. Tumors that are attached to the skin often are cancerous, whereas tumors that can be moved by applying pressure are more likely to be benign.

Detection: The tumors can be seen as swollen pea-sized growths on the mammary glands. Conduct a simple touch test and look out for abnormally hard swellings under the skin.

2. Testicular Tumors

Testicles that are enlarged, or the presence of one testicle that is larger than another, is often a likely tip-off to testicular cancer. If you notice any change in the shape of a dog’s testicles, get in touch with a vet for an examination. Note that dogs with undescended testicles are very likely to develop testicular cancer, so if that is the case with your dog, be vigilant to swelling of the descended testicle or your dog’s abdomen. Neutered dogs can’t develop testicular cancer.

Detection: Testicular Tumor is marked by noticeably enlarged testicles. Swelling can occur in either one or both testicles.

3. Mast Cell Tumors

One of the most common skin tumors in dogs, mast cell tumors are raised growths that appear on your dog’s skin. Tumors caused by mast cells are cancerous. Vets can determine if a lump on your dog’s skin is the result of mast cell growth through a needle aspiration of the lump.

Detection: Easily noticeable wart-like growths that are soft to the touch. There is usually one single growth in one area instead of a cluster of bumps. Only 11 to 15 percent of dogs have more than one MCT growth.

4. Histiocytoma

If you spot a bright red hairless bump on your dog’s skin, you may feel alarmed, particularly since histiocytomas often appear overnight. The good news is that histiocytoma tumors are benign. However, as with any bumps, it’s always recommended that you have a vet inspect and diagnose the issue.

Detection: Painless and hairless bumps commonly occur on the ears, head, or legs. These bumps have a tendency to grow rapidly in the first month.

5. Hemangiosarcoma

These cancerous tumors occur from blood cells and they commonly appear in internal organs like the liver and heart. However, hemangiosarcoma can also occur on a dog’s skin. Most commonly, hemangiosarcomas on the skin will appear on a dog’s hind legs or neck, or any body part that is hairless. They are very often red or black in color and can be treated with a combination of surgery and chemotherapy.

Detection: Hard and dark-colored growths that usually occur on a dog’s hind legs. Tumors can change in size due to internal bleeding. These tumors do not cause skin ulcerations.

6. Melanoma

Melanomas are dark brown or black in color and they look a lot like a mole. These marks can appear on the eyelids, nail bed, mouth, or skin. While some are benign, others are malignant, so it’s important to check in with the vet since appearance alone cannot reveal if the tumor is malignant or benign.

Detection: Benign melanomas are usually round dark-colored masses often occurring on the head, back, and paws. Malignant melanomas are ones that spread rapidly.

7. Lipoma

These fatty skin tumors are benign and appear in the subcutaneous layer of a dog’s skin. These tumors have a soft feel and can be moved by applying pressure.

Detection: Lipomas are usually soft lumps underneath the skin that move ever so slightly when touched. These lumps are usually seen occurring under the armpits, neck or belly.

8. Basal Cell Tumors

These tumors are quite common in dogs. Often times a single basal cell tumor is seen as opposed to multiple growths. The size of the tumors vary and they are usually hairless and raised above the skin. You’ll spot these tumors on a dog’s neck or shoulders. Generally, they are not malignant and can be surgically removed.

Detection: Measuring 1 to 10 centimeters, these lumps are usually pigmented and they typically occur on the head, neck, shoulders, or leg. Basal cell tumors may ulcerate and can thus be painful.

9. Squamous Cell Carcinoma

These tumors are a result of sun exposure and generally occur in hairless areas on your dog’s skin. They appear to have various different colors, including red, white, or gray. More often than not, these tumors are malignant and thus need surgical intervention.

Detection: These sores occur in areas with light-colored fur or places where there is no hair. The growths are usually flaky and prone to bleeding. Growths can occur on the nose, scrotum, legs, and paws.

10. Lymphoma

Also known as lymphosarcoma, this cancer of the lymph nodes has several classification types. Multicentric lymphoma is the most common variety of tumors in dogs. It’s characterized by swollen glands in the dog’s neck. Although there is no cure for lymphoma, chemotherapy can be used to reduce symptoms and extend a dog’s life.

Detection: Multicentric Lymphoma tumors typically have a rubbery texture and they move freely under the skin.

Keep an eye out for growth and swollen areas on your dog. While some growths are benign and can be ignored without a second thought, it’s always a good idea to get every lump checked by a veterinarian.

Dog Skin Cancer - When Is a Tumor Malignant?

Skin tumors are the most common tumors found in dogs. Some breeds, such as Boxers and Retrievers, are at a higher risk of having a skin tumor in their adult or senior years. Dog skin cancer is not always a given, though. Tumors may be benign (non-spreading or non-cancerous) or malignant (cancerous), but any lump should be looked at by a veterinarian.

Not all skin tumors may be caused by the sun, but sun exposure can increase the chances of developing tumors, especially if your dog has light-colored fur. Areas that aren't covered by fur, like the nose and paw pads, are at greater risk of sun damage. You can take some steps to help prevent it, but the best defense against skin cancer is early detection, so talk to your vet immediately after finding any lumps.

Is it dog skin Cancer?

Certain skin problems can be mistaken for skin cancer. Some of them can be just as serious as cancer, so any questionable lump or growth should be examined and treated.

  • Benign Tumor: Sometimes tumors are not cancerous, but they may still need to be removed.
  • Fungal Infection: Ringworm and blastomycosis can cause skin lesions or significant irritation. Ringworm is highly contagious, and blastomycosis can cause significant lung damage so it is important to treat either infection as quickly as possible.
  • Allergic Reaction: Some allergic reactions, such as eosinophilic granuloma (although rare for dogs), can cause raised ulcers, especially on the mouth, face, feet and thighs.

If a tumor seems to be growing, or is an open wound that isn't healing, it’s more likely that the tumor is cancerous. Either way, make sure to have every tumor examined by a vet. They’ll be able to give you an exact diagnosis with a biopsy and other lab tests, and will likely recommend surgical removal and additional treatment, especially if the tumor is malignant.

Most Common Types of Skin Tumors in Dogs

Several skin tumor types are commonly found in dogs, and their prevalence has allowed vets to develop specialized treatments to best extend length and quality of life. If detected and removed early, some dogs can recover completely from some kinds of skin tumors. Other tumors may require more aggressive treatment, which can become very expensive.

  • Mast Cell Tumors: Mast cell tumors are the most common malignant tumors for dogs, and are usually solitary lumps found on the body or legs. Breeds that are at risk include BeaglesBoston Terriers, Boxers, Labrador RetrieversPugs, and Schnauzers. One strange side effect of the tumor is an increase in stomach acid and in likelihood for developing gastric ulcers. Since these tumors spread easily, vets will often start with surgical removal, but the use of radiation and chemotherapy has aslo been used to fight mast cell tumors.

  • Basal Cell Tumor: This form of tumor is one of the most common in animals, and among dogs, is often found in Cocker Spaniels and Poodles. These tumors grow from deep skin layers and can be seen as a single hairless lump on the head, neck, or shoulders. It is unlikely they will be malignant and there is low risk of spreading, so after freezing or surgical removal, many dogs recover completely.

  • Melanoma: Melanomas are often seen as a darkened area, sometimes looking like an overgrown or raised mole. They can be found on the mouth or mucous membranes, or in areas with hair -- even in the toes of black dogs. Melanomas grow very quickly, especially with sun exposure or licking, and can easily spread to the lungs and liver if not treated quickly. More than some other, slower growing tumors, melanomas are likely to require radiation or chemotherapy in addition to surgical removal.

  • Squamous Cell Carcinoma: This tumor is usually firm and raised, sometimes mistaken for a wart, and found on the abdomen or genitals. Basset Hounds, Beagles, Bull TerriersColliesDalmatiansKeeshonds, Schnauzers, and other dogs with short coats are at risk. This tumor has been linked to sun exposure and possibly also the papilloma virus. While it is unlikely to spread to organs, it can still cause significant damage to surrounding tissue.

  • Hemanglosarcoma: This malignant tumor grows from blood cells, appearing as a raised, bruised lump (or multiple lumps) on the hind legs or abdomen. The lumps may change in size or color but are often firm and malleable. Boxers, English SettersGerman ShepherdsGolden RetrieversPit BullsWhippets, and older dogs are more likely to have hemanglosarcoma. These tumors are more likely to metastasize (spread to new areas or organs), and sun exposure for light-colored dogs may have a predisposition to getting hemanglosarcoma. This tumor will require surgical removal and probably ongoing radiation therapy because it is so aggressive. Unfortunately, it usually shortens a dog's lifespan.

Frequently Asked Questions

What does a cancerous lesion look like on a dog?

Veterinarians advise the following signs. One may feel firm, raised wart-like blemishes that are squamous cell carcinoma. One may see rubber-like, inflamed sores that are mast cell tumors. Melanomas can look like strange-colored lumps or bumps on the lips, mouth, pads of feet, or toenail beds. Dog owners may see other pain symptoms, such as limps.

What does a cancerous spot look like?

The National Health Society (NHS) says cancerous lumps are red, firm, and sometimes turn into ulcers. Other cancerous patches are usually flat and scaly. Exposed areas of the skin can show non-melanoma skin cancer, but it is still important to ask your physician for an emergency check-up.

What does canine melanoma look like?

The American Kennel Club (AKC) tells dog owners to watch out for canine melanoma that may hide under their fur, around the mouth, within their nailbeds, etc. Look out for raised, ulcerated lumps that may be malignant melanomas. Look for gray or pink lumps around the mouth. Toe swelling, loss of toenails itself, and even destroyed underlying toe bone can be nail bed malignant melanomas.

How do you tell if a mass on a dog is cancerous?

You can identify a potentially cancerous mass on your dog via touch. Does the spot feel firm, rubbery, bumpy, or scaly? Does the spot look red, wart-like, or strange-colored? Even a soft and fatty spot can be a lipoma, which is not cancerous. Veterinarians still recommend making an appointment if you have any questions or worries!

More on Cancer In Dogs

Cancer in Dogs and Cats
Bone Cancer in Cats and Dogs
Cancer Drugs for Dogs -- What Are Your Options?

This information is for informational purposes only and is not meant as a substitute for the professional advice of, or diagnosis or treatment by, your veterinarian with respect to your pet. It has, however, been verified by a licensed veterinarian for accuracy.

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