Vet-Verified Guide to Dog Skin Cancer: Symptoms, Causes, and Treatment

Imagine you're brushing or petting your beloved dog when you suddenly feel an unusual lump or bump on their skin. Don't panic! Many of these lumps can be harmless, like bug bites or skin rashes. However, it's always a good idea to consult your vet if the lump doesn’t go away or looks unusual.

Did you know that the most common skin tumors are benign?

In some cases, skin cancers, such as melanoma, can appear as dark-colored or black spots on your dog's skin. The good news is that in 60-80% of cases, skin lumps in dogs are benign tumors and unlikely to develop into cancer. Still, it’s essential to consult your vet for an accurate diagnosis and peace of mind.

So, if you notice a scab, bump, black spot, or lump on your dog's skin, it’s often not a major cause for concern. However, appearance alone isn’t enough to tell if your dog has skin cancer, so it’s important to take them to the vet as soon as possible for a proper diagnosis.

Still searching for a comprehensive guide on skin cancer in dogs?

In this article, you'll learn the key signs of malignant skin cancer in dogs, as well as the potential causes of this serious condition. We’ll guide you through everything you need to know to help keep your pet healthy and safe.

What Exactly is Dog Skin Cancer?

Skin cancer occurs when healthy skin cells begin to grow abnormally, often due to factors like certain viruses, prolonged sun exposure, hormonal imbalances, or exposure to harmful chemicals in the environment.

Skin cancer is a fairly common condition in dogs, and can result in both malignant (cancerous) tumors, such as squamous cell carcinomas, and benign (non-cancerous) tumors, like lipomas. Early detection is crucial for successful treatment and improving your dog’s life expectancy.

What Are the Potential Causes of Skin Cancer In Dogs?

Skin cancer in dogs can be caused by a variety of factors, but modern veterinary medicine has not yet pinpointed an exact cause. Below are some of the most commonly associated factors that may contribute to this condition:

Sun exposure

The most common type of cancer caused by sun exposure is squamous cell carcinoma (SCC). Dog breeds with short fur or light skin are more vulnerable to this cancer because they have less protection from UV rays.

SCC often occurs in areas with little or no hair, such as the ears, nose, and eyelids. White dogs are at even greater risk. Dog breeds typically affected with squamous cell carcinomas include Basset Hounds, Collies, Dalmatians, Beagles, Bull Terriers, and others. Be sure to monitor these areas on your dog and consult a vet if you notice any unusual changes.

Genetics

Some dog breeds are more prone to certain types of skin cancer like malignant melanomas. For example, Beagles, Boxers, Pugs, Boston Terriers, Labradors, and Shar-Peis are more susceptible to mast cell tumors, likely due to genetic factors. If you own one of these breeds, it's important to regularly check for unusual lumps and consult your vet if you notice any changes.

Skin trauma

Wounds that do not heal and scars from skin trauma can increase the risk of skin cancer in dogs, likely due to chronic inflammation or repeated cell damage. If your dog has any non-healing wounds, it's important to consult your vet for proper care and monitoring, as these could be early indicators of common skin tumors.

Chronic skin irritations

You might be surprised to learn that allergies and compulsive behaviors, like overgrooming, excessive licking, and scratching, can lead to skin irritations. Over time, these chronic irritations can increase the risk of developing skin cancer in dogs.

The Clinical Signs of Dog Skin Cancer

Skin cancer in canines can present in various forms, ranging from small red or black spots to large, cauliflower-like growths. These may or may not be accompanied by an odor. Here's what to watch for if you suspect your dog may have skin cancer:

• Lumps or bumps of various sizes
• Nodules
• Red areas
• Black spots or growths
• Red spots or growths
• Crusts or scabs
• Sores
• Hyperpigmentation
• Skin ulcers
• Unpleasant skin odor
• Wounds that won’t heal at all or have delayed healing
• Lesions that have hardened, irregular edges
• Abnormal discharge

If the malignant skin cancer has metastasized to other organs, you may observe additional clinical signs beyond those affecting the skin:

• Coughing
• Difficulty breathing
• Weight loss
• Low appetite
• Lethargy
• Low energy (your dog refuses to play and sleeps almost all day long)
• Changed behavior

The time you spend with your beloved friend petting, brushing, or washing should give you the perfect opportunity to check their skin for external parasites, tumors, or any other "things" that should not be on your dog's skin. The sooner you diagnose skin cancer, the better it will be for your pet!

Types of Skin Cancer in Dogs

Before we continue, it’s important to clarify that the term "skin cancer in dogs" does not refer to a single condition. Instead, it serves as an umbrella term encompassing several potential health issues. These are outlined below:

Squamous Cell Carcinoma (SCC)

Squamous cell carcinoma is a malignant tumor, meaning it has the potential to spread to other organs (a process known as metastasis) and pose a significant risk to your dog's life. Though relatively rare, accounting for only 5% of all skin tumors, this type of cancer develops in the outermost layer of a dog's skin, the epidermis.

SCC typically occurs in older dogs and appears as a firm, raised, wart-like lump that is often ulcerated. The most common areas for this type of cancer to develop on a dog's body include:

• Lower legs
• Head
• Abdomen
• Back

This type of cancer can also develop in your dog’s nail beds or mouth. When SCC occurs in the mouth, it is often mistaken for other conditions, such as gingivitis, mouth ulcers, or dental diseases.

Squamous cell carcinoma generally develops in areas with sparse hair, hairless regions, or fair skin. Dogs with short fur that spend a lot of time outdoors, where they are exposed to sunlight, have a higher incidence of SCC.

Certain breeds are at higher risk of developing squamous cell carcinoma:

• Boxer
• Beagle
• Bull Terrier
• Keeshonds
• Schnauzers
• Bloodhound
• Basset Hound
• Standard Poodle
• Golden Retriever
• Labrador Retriever
• Norwegian Elkhound
• American Pit Bull Terrier
• German Shorthaired Pointer

The diagnosis begins with a thorough examination of the skin lesions by the veterinarian. If SCC is suspected, the veterinarian may recommend a cytological or histopathological examination. For cytology, cells are extracted from the tumor using a fine needle, a technique known as fine needle aspiration (FNA).

In a histopathological exam, the veterinarian will remove part or all of the tumor and send it to a lab for diagnosis. In some cases, advanced diagnostic techniques such as CT scans may be recommended to determine the extent of the disease and the precise location of the tumor, particularly when SCC affects areas like the mouth.

Treatment typically involves surgery to remove the skin tumor. In cases where complete removal isn't possible, radiation therapy or chemotherapy may be used to help prevent recurrence. Fortunately, SCC rarely spreads to the lymph nodes or lungs, meaning metastasis is uncommon.

However, some dogs may develop multiple skin tumors, which can be challenging to manage. Affected dogs may also require oral or topical medications to help control symptoms or support treatment.

Mast Cell Tumors

Mast cells are part of the immune system and play a key role in allergic reactions. They are distributed throughout the body, with a higher concentration in the skin.

Additionally, mast cell tumors in dogs are often referred to as the "chameleons" of skin tumors due to their varied appearance. They may appear as single or multiple growths on the skin, taking the form of a whitish nodule, cyst, reddish nodule, or papilloma. These tumors are frequently mistaken for lipomas, which are benign fatty tissue tumors.

The following dog breeds have an increased risk of developing mast cell tumors:

• Boston terrier
• Boxer
• Bulldog
• Golden retriever
• Labrador retriever
• Pug

Diagnosis is typically made through fine needle aspiration, a generally painless procedure.

Treatment involves surgical removal of the tumor, which is then sent to a pathologist for grading. Mast cell tumors are graded on a scale of I to III, with Grade I tumors having a very low risk of metastasis and Grade III tumors having a much higher risk, which is associated with greater mortality.

For high-grade tumors, additional treatments such as radiotherapy and chemotherapy are recommended alongside surgery to help prolong the pet's life.

Malignant Melanoma

In dogs, unlike in humans, most diagnosed melanomas are benign (non-cancerous). Additionally, melanoma in dogs is less influenced by UV exposure compared to humans. Malignant melanoma typically occurs in dark-colored dogs, such as those with black, dark brown, or mixed coats, and it is more common in older dogs than in younger ones.

Melanoma originates in melanocytes, the epidermal cells that produce melanin. These tumors are usually large and may be elevated or flat. Most owners initially notice them as a black spot on their dog's skin.

While malignant melanoma can develop in all dog breeds, certain breeds are more predisposed to it. These breeds include:

• Boston Terrier
• Chihuahua
• Doberman Pinscher
• Giant and Miniature Schnauzer
• Golden Retriever
• Gordon Setter
• Irish Setter
• Irish Terrier

The diagnosis is typically made through fine needle aspiration or biopsy, where the tumor is removed and sent to the lab to analyze the cell types involved. A biopsy is also essential for distinguishing between benign and malignant melanoma. To determine the extent of the melanoma, additional diagnostic methods may be required, such as:

• Fine needle aspiration of the lymph nodes
• Chest X-rays
• Abdominal ultrasound

In some cases, diagnostic imaging, such as CT or MRI, may be recommended by your veterinarian. These imaging techniques can help determine the extent of the cancer, enabling the veterinarian to select the most appropriate treatment.

Unfortunately, the prognosis for malignant melanoma is guarded due to its aggressive nature, as it often spreads to nearby lymph nodes or even the lungs.

Given the cancer's aggressive behavior, treatment typically includes surgical removal of the tumor and/or radiotherapy. In addition, immunotherapy (such as the melanoma vaccine) and/or chemotherapy may be recommended. However, chemotherapy has limited effectiveness, with only about 30% of patients responding to treatment.

Epitheliotropic Lymphoma

Cutaneous lymphoma is a less common type of cancer, with the epitheliotropic form usually originating from T-cells. This form diffusely affects the skin and can quickly progress to systemic involvement. The clinical signs include extensive, ulcerated skin lesions, which are often secondarily infected.

Epitheliotropic lymphoma may initially resemble general skin inflammation but often progresses to single or multiple skin nodules and non-healing wounds that fail to respond to standard treatments. Certain breeds, such as English Cocker Spaniels and Boxers, are particularly predisposed to developing this form of lymphoma.

Diagnosis is made through a skin biopsy, where small skin sections—especially from nodules or wounds—are removed and sent to a laboratory for analysis. The prognosis for this type of skin cancer is generally poor, with most dogs surviving 5 to 10 months after diagnosis. However, in rare cases, some affected dogs have survived for several years.

For a single lesion, treatment may consist of surgical removal combined with radiotherapy. In cases with multiple lesions, the preferred treatment involves administering a combination of chemotherapy drugs.

Hemangiosarcoma

This type of cancer develops from the cells that line the blood vessels in the dog's body. When affecting the skin, hemangiosarcoma can present in two forms: dermal (on the skin surface) and subcutaneous (under the skin).

Dermal hemangiosarcomas typically appear as red-black growths that may eventually ulcerate and bleed. Approximately one-third of these tumors can spread to internal organs, making early diagnosis critical.

Subcutaneous hemangiosarcoma typically feels like a lump beneath the dog’s skin, with the surface appearing normal. This form of hemangiosarcoma can also spread to internal organs, making prompt diagnosis and treatment important.

Certain dog breeds are at a higher risk of developing hemangiosarcoma. These include:

• Boxers
• Doberman pinschers
• English setters
• German shepherds
• Golden retrievers
• Labrador retrievers

As with other cancers, dermal and subcutaneous hemangiosarcoma are diagnosed through fine needle aspiration or biopsy. Early detection is crucial for your dog’s health, so it’s recommended to visit your veterinarian as soon as you notice any lumps, bumps, or red and black spots on their skin.

For these types of cancer, chest X-rays and abdominal ultrasounds are also recommended to determine whether the cancer has spread to other areas of the body.

For dermal hemangiosarcoma, surgical removal of the tumor can be curative if the cancer is diagnosed early. In some cases, chemotherapy may also be recommended. For subcutaneous hemangiosarcoma, a combination of surgery, chemotherapy, and/or radiotherapy is typically advised.

How Long Can a Dog Live with Skin Cancer?

The life expectancy of a dog with skin cancer depends on the type of cancer. In general, dogs with skin cancer may live anywhere from a few months to several years, depending on the diagnosis.

For instance, dogs diagnosed with malignant melanoma typically have a life expectancy of two to ten months, whereas those with dermal hemangiosarcoma may live for up to two years. In cases of squamous cell carcinoma, life expectancy ranges from 19 to 43 months following surgical removal of the tumor.

We understand that a cancer diagnosis can be overwhelming and challenging. That’s why it’s crucial to regularly examine your dog’s skin and seek veterinary attention immediately if you notice any lumps, bumps, or red or black spots. Early diagnosis and treatment are key to ensuring the best possible outcome for your pet.

Can Skin Cancer in Dogs Be Treated Naturally?

Has your veterinarian confirmed that the nodules, lumps, bumps, or black spots on your dog's skin are cancerous? If so, providing the best possible treatment for your dog is essential. At Zumalka, we offer natural products designed to support your dog's health and help them fight against skin cancer.

PIPTOPET is a natural product with numerous health benefits for pets suffering from illness. Its key ingredient, a medicinal mushroom called Fomitopsis betulina (formerly Piptoporus betulinus), has been scientifically proven to offer anti-inflammatory, anti-tumoral, antibacterial, and antiviral properties, as demonstrated in studies on mice, monkeys, and dogs.

Additionally, combining homeopathic treatments like PIPTOPET with surgical removal of cancerous tumors may help improve your dog's life expectancy.

About the author

Dr. Iuliana Mihai, DVM, MSc, PhD

Iuliana Mihai, DVM, MSc, PhD, is a Bucharest-based veterinary expert specializing in internal medicine and oncology.

Her work has been published in reputable publications such as Veterinary Medicine Journal, Catster.com, Dogster.com, Hepper.com, Meowiz.com, Springnaturals.com, Petkeen.com, and Wilderharrier.com.

She is a malpractice and negligence veterinary consultant and a graduate of The University of Agronomic Sciences and Veterinary Medicine and The Romanian Academy.

Read the complete profile of Dr. Iuliana Mihai, DVM, MSc, PhD (Veterinarian) here.