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Pigmented lumps or black lumps on dog skin can cause pet parents to panic. The concern often stems from how human medicine has educated us about our dangers of skin cancer. This is correct since, just as with people, dogs can also get skin cancer.

The most dangerous cause of a pigmented lump or bump on the skin is melanoma. First, let’s look at all the possible causes of black lumps in dogs and then we will offer additional information about melanomas.

Causes of Pigmented or Black Lumps on Dogs

There are many possible causes for pigmented or black lumps on dogs. They include:

• Ticks – A tick can be confused with a pigmented lump or black bump. Ticks are irritating arthropods that prey on dogs and attach themselves to the skin as they take their blood meals. Veterinarians commonly remove ticks from dogs that were mistaken for small-pigmented skin lumps. Learn more about how to remove a tick from a dog.
• Scabs – A scab is a rough, dry crust that forms as a protective barrier over a healing cut, laceration, puncture, or wound. Scabs can be large or small and are often pigmented. Clipping the hair and careful close examination can usually reveal that a pigmentation is a scab and not a tumor.
• Foreign bodies – Something caught in the hair next to the skin can be mistaken for a pigmented lump. For example, this can be dried chewing gum, food, or a plant burr.
• Insect bites – A bite, such as one from a wasp, bee, or spide,r can cause local skin inflammation that appears as a pigmented bump.
• Punctures – A puncture can appear as a black bump in dogs. Punctures can occur from trauma or from a bite wound from another animal.
• Abscesses – An abscess is a localized pocket of infection that contains pus. The skin over the abscess is generally abnormal in color, and can range from red to bruised/black. Punctures or bites can turn into abscesses. Clipping and cleaning the area will often reveal if an abscess is the underlying cause of the skin pigmentation.
• Warts – Canine viral papilloma, also known as dog warts, are one of the most common causes of small lumps in dogs.  They are generally raised and look like small pale cauliflower bumps. Most warts are pale in color although, when infected or traumatized, many will appear dark from the inflammation or blood. Some dogs will also lick these lesions, which causes additional pigmentation to the wart and the hair around it. This is most noticeable in white- or light-haired dogs. These benign masses are generally not a concern, but can break open, become nicked during grooming, or become infected. For these reasons, some dog warts are surgically removed. Surgical removal can be curative, though more warts may form elsewhere on the body.
• Histiocytomas – A histiocytoma is a small, raised lump that primarily occurs on young dogs under three years of age. They most often occur on the face and legs. Some dogs will lick at histiocytomas, which can cause a pigmented appearance. These are benign and often spontaneously resolve.
• Blisters – A blister is a small fluid-filled bubble on the skin most often caused by friction, burning, or other damage. They can appear as pink raised lesions or have pigmentation if there is blood inside the lesion.
• Cysts – A sebaceous cyst is a small sac containing an accumulation of secretions produced by the sebaceous glands. These can appear as small bumps and are considered benign, but may become open and infected. They can be red or appear pigmented. Most sebaceous cysts do not require treatment.
• Hematoma – A hematoma is a bruise that can be blue to black in color. Most often this is associated with some trauma, such as being hit by a car or other wound. Bruising can also occur from abnormal bleeding disorders. Learn more about bruising and bleeding in dogs.
• Mast cell tumors (MCT) – Mast cell tumors account for approximately 20% of all skin tumors that occur in dogs. They are commonly lumps in or just under the skin. Some dogs can have multiple masses that occur at the same time. MCT can occur anywhere on the body. Some MCT causes dogs to itch or lick, which can cause discoloration of the mass. Some dogs can have additional signs of illness such as weight loss, vomiting, and/or diarrhea from the compounds released by the tumor. It is important to diagnose this type of tumor early and have proper treatment.
• Malignant melanomas – This is a type of skin cancer that affects pigmented cells known as melanocytes. Because the underlying cells are generated from pigmented cells, the masses are generally brown or black in color. Tumors from melanocytes occur anywhere on the body including areas in the mouth, mucous membranes, and nail beds. Many melanomas are known to grow quickly and can spread to organs such as the lymph nodes, liver, and/or lungs. It is important to diagnose this type of pigmented tumor as soon as possible. There are various treatment options available, including a DNA tumor vaccine.

How to Determine the Cause of a Black Lump on a Dog

If your dog has a pigmented lump, the best way to help determine the underlying cause is to closely examine the lump. Your veterinarian may provide the following care during an appointment:

• A complete examination. A complete examination of your dog, looking at the eyes, ears, listening to the lungs and heart, feeling the lymph nodes, and feeling the abdomen to evaluate the size and shape of the kidneys, liver, spleen, bladder, and intestines.
• Examination of the black skin lump. Your vet will evaluate the skin mass noting the size, shape, depth, texture, location, and color. Shaving hair around that area will help evaluate the pigmented lump and surrounding skin. This may be best done with the help of your veterinarian.
• Provide recommendations. Based on the size, location of the mass, pigmentation, and suspicion that this lump could be cancerous, your vet will provide recommendations as to the best approach to determine the cause of the skin mass. They may recommend evaluating the mass with a fine needle aspirate, biopsy, or mass removal called “lumpectomy”.  If their level of concern about the mass is high, they will recommend sending a tissue sample to a laboratory for histopathology.

Treatment of Black Lumps on Dogs

Treatment recommendations will be determined by the underlying cause of the bump. An abscess may be drained, ticks may be removed, and skin infections may be treated with antibiotics. For pigmented skin masses that are determined to be skin cancer, recommendations will depend on the type of cancer. Possible treatments may include some combination of surgical removal of the pigmented bump, radiation therapy, and/or immunotherapy.

We hope this article helps you better understand the causes of some pigmented lumps in dogs.

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