Pet owners may pet or groom their dog to suddenly feel a hard lump on their dog that they have not felt before. This can cause concern, and in some cases, downright panic.  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.

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 and huge. 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 have only the color of the skin and other skin lumps on the skin 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 one of the tumors of concern 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 in Dogs
• Lipoma (Fatty Tumor) in Dogs
• Malignant Melanoma in Dogs
• Mammary Gland Tumors
• Mast Cell Tumor in Dogs
• 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 may be nothing to worry about or it may be something that you should be concerned about. 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.

Here are a couple possibilities of what your veterinarian may do:

• Complete exam. Your vet will likely perform a complete examination looking at your dog’s eyes, ears, look in the mouth, listen to the heart, and feel the abdomen.
• Examine 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.
• Provide 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 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 tests to evaluate the lump may include:

• 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 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.

We hope this article helps you better understand what different lumps and bumps on your dog’s skin are, when to see your veterinarian, and what your veterinarian may do to help determine the type of lump.

Additional Articles of Interest Relating to Hard Lump on Dog:

• What Small Bumps on Dogs Can Mean
• What Large Bumps on Dogs Can Mean
• Fatty Cysts in Dogs
• What Does a Black Lump on a Dog’s Skin Mean?
• Canine Cancer – What Are the Warning Signs?
• Lipoma (Fatty Tumor) in Dogs
• Lumpectomy in Dogs
• Metastatic Neoplasia (Cancer) in Dogs
• Skin Cancer in Dogs
• Transmissible Venereal Tumor in Dogs
• What to do if Your Dog Has a Skin Tag