I Found a Hard Lump on My Dog — What is It?

Suddenly feeling a lump while petting or grooming your dog can be quite the surprise, likely causing dismay, if not outright shock.

A lump (also referred to as a mass, growth, bump, or tumor) can occur anywhere on the body and come in all shapes and sizes. Some hard lumps on dogs can be benign and others malignant. In this article, will review the possible causes for hard lumps on dogs and offer recommendations for what you should do.

How to Describe a Lump on a Dog

There are many ways to describe a skin lump on a dog. The size, shape, texture, color, location, depth, and rate of growth are all characteristics that can help determine what kind of lump it is and what level of concern you should have.

Ways to describe a hard lump on a dog include:

Size. Dog lumps can range from very small to enormous. In fact – some tumors, such as lipomas (also known as fatty tumor) in dogs, can weigh several pounds. Learn more about What Small Bumps on Dogs Can Mean and What Large Bumps on Dogs Can Mean.
Shape. Some dog lumps can be regular and others can be irregular. For example, most lipomas are round in shape.
Texture. Some dog lumps are firm and some are soft. Some tumors can have both components with part being soft and part firm. Lumps that are commonly soft are fatty tumors. Learn more about Fatty Cysts in Dogs.
Color. Some hard dog lumps are under the skin and are skin-colored, while other skin lumps can white, red (if inflamed), or pigmented brown or black. Learn more about What Does a Black Lump on a Dog’s Skin Mean?
Location. Lumps can occur anywhere on the body. Most lumps that pet owners feel are on the skin, however, lumps can also occur on organs, such as on the liver, spleen, and/or kidney. Skin lumps in dogs can grow on top of the head, neck, chest, body wall, axillae, legs, tail, and just about anywhere else. Hard lumps that involve the mammary chain (breast) are concerning and should be evaluated immediately.
Depth. Skin lumps can be on the skin (such as a mole or skin tag) or they can be under the skin. Lumps that are under the skin can be attached or moveable.
Rate of growth. Lumps in dogs can grow at varying rates. Some lumps grow very quickly, even over days or weeks, and some grow very slowly over months to years. Histiocytomas and Mast Cell Tumors are two types of fast-growing tumors. Fatty tumors tend to grow slowly.
Other. Some skin lumps can be ulcerated or even become infected. This can result from trauma to the mass, poor blood supply to the tumor causing necrosis of the tumor, or be associated with certain types of cancer. Histiocytomas or Mast Cell Tumor can be itchy to some dogs.

These tumor characteristics can help guide your veterinarian as to what the hard lump on your dog may be. For example, many dogs get fatty tumors that can occur anywhere, but are soft and commonly attached to the body wall. Fatty tumors are rarely firm and are uncommon on certain locations, such as on top of the head. A large tumor that involves the mammary chain (breast) can be suggestive of cancer.

Another factor that is commonly considered when evaluating the cause and concern for a tumor is the age of the dog. Some hard lumps are more common in young dogs such as Histiocytomas. While young dogs (under three years of age) are more likely to get histiocytomas (especially on the face and extremities), they can happen to dogs of any age in just about any location. Other types of tumors are more common in an older dog, such as mast cell tumors, lipomas, skin cancer tumors, and breast cancer.

What Is this Hard Lump on My Dog?

Most dog owners worry that a hard lump could be skin cancer. Skin cancer in dogs encompasses a broad category of tumors that includes any uncontrolled growth of cells of the skin or associated structures such as glands, hair follicles, and supportive tissues (fat and connective tissue). The skin is the most common site of cancer in dogs. Skin cancer frequently occurs in dogs between 6 to 14 years of age, but can occur at any age.

Some common tumors that appear in or on the skin in dogs include:

Canine Viral Papillomas (Dog Warts)
Ear Tumors
Histiocytoma
Lipoma (Fatty Tumor)
Malignant Melanoma
Mammary Gland Tumors
Mast Cell Tumor
Tumors of the Penis and Prepuce
Metastasis to the skin from tumors elsewhere in the body can occur, but these are not considered skin tumors because they did not start in the skin. Learn more about skin cancer in dogs and metastatic neoplasia (cancer) in dogs.

What Should You Do if You Find a Hard Lump on Dog?

If you find a hard lump on your dog, the best thing to do is to see your veterinarian to help you determine what it is. It is often impossible to positively diagnose the underlying type of tumor without laboratory testing. Your vet can make recommendations to guide you on treatment options.

Common Examinations and Recommendations

Complete exam. Your vet will likely perform a complete examination, looking at your dog’s eyes, ears, mouth, listening to the heart, and feeling the abdomen.
Examination of the skin mass. Your veterinarian will evaluate the skin mass, noting the characteristics described above, including size, shape, depth, consistency, location, color, and more. They will also feel your dog all over to see if there are additional bumps.
Make recommendations. Based on the characteristics and location of the tumor, your vet will offer recommendations as to the best approach to your dog’s hard skin bump. Recommendations may be blood work, urinalysis, tissue samples to evaluate the mass, and/or surgical removal of the mass:
Assess general health with blood work and urine. Laboratory work including a Complete Blood Count (CBC), Biochemical Profile (sometimes call the blood chemistry), and urinalysis can help evaluate overall health and look for common underlying problems, such as infections, anemia, kidney disease, liver problems, diabetes, and more.

Additional Testing

Fine needle aspirate (FNA). This procedure involves placing a small needle into the mass and aspirating back cells with a syringe. The cells are placed on the slide that is allowed to dry, stained, and examined under a microscope. The cells are evaluated by looking for abnormal cells that can be a sign of cancer.
Biopsy. A biopsy is a procedure to obtain a larger sample of a mass for microscopic analysis. A bigger sample is often a better sample. This procedure most often requires general anesthesia.
Chest radiograph (x-ray). An x-ray may be recommended if your dog is showing respiratory symptoms, such as trouble breathing or coughing, or if there is concern that a tumor could be cancerous with possible spread to the lungs.
Mass removal. The procedure of a lump removal is also called “lumpectomy”. Removing a mass most often requires general anesthesia.
Histopathology. After obtaining a sample of the tumor or removing the tumor, a sample is sent for additional testing at a laboratory to determine the presence or absence of disease. If the laboratory determines the sample is abnormal, they will identify the type and severity of the disease.