What Does Cancerous Lump On Dog Feel Like?

Cancerous lumps in dogs are one of the most common types of tumors seen in veterinary medicine. According to research published in PLOS One, the lifetime prevalence of malignant tumors in dogs is 29.7 per 1000 dogs (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10089278/). Though benign tumors are more common, malignant tumors can be very serious if not treated properly. Cancerous lumps can appear on the skin or internally, with some of the most common forms being mammary tumors, mast cell tumors, melanoma, and soft tissue sarcomas.

Detecting cancerous lumps early is critical for successful treatment and prognosis. Lumps that are allowed to grow untreated have a higher chance of metastasis and lower survival rate. Owners should monitor their dog’s body frequently and alert their veterinarian about any new lumps, bumps, or growths. With early intervention, many dogs can undergo treatment and live happily for years following a cancer diagnosis.

Types of Cancerous Lumps

Some of the most common types of cancerous lumps found in dogs include:

Mast Cell Tumors

Mast cell tumors are a very common form of skin cancer in dogs. According to the University of Wisconsin Veterinary Care, mast cell tumors account for up to 20% of all skin tumors found in dogs [1]. These tumors often first appear as raised lumps on the skin and can be red in color. They may bleed or ulcerate as they grow larger. Mast cell tumors can develop anywhere on the body and vary in their degree of aggression.


Lipomas are benign fatty tumors that grow under the skin. They are very common lumps found in older dogs, especially on the torso. Lipomas start out soft and movable under the skin, but can become firmer over time. Though usually benign, in rare cases they can interfere with organ function depending on their size and location [2].


Hemangiomas are benign tumors made up of blood vessels. They often first appear as small red or bluish lumps under the skin that continue to grow over time. Hemangiomas rarely turn cancerous, but can rupture and bleed if they develop on thin areas of skin [2].


Cancerous lumps on dogs can develop anywhere on the body, but certain locations are more common than others. According to the Knutsford Vet Surgery, some of the most common locations for cancerous lumps in dogs include the skin, mammary glands, testicles, mouth, and bones.

The skin is one of the most frequent sites for cancerous lumps, especially the head, back, and legs. Other common locations are the breasts and mammary glands in female dogs. Testicular cancer is also relatively prevalent in male dogs, appearing as lumps on the testes.

Less frequent areas for cancerous masses include the mouth (potentially affecting the gums, tongue, lips), bones (resulting in bone cancer), and internal organs like the spleen, liver, and kidneys. Lumps inside the abdomen or chest may signal cancers inside the body rather than on the skin.

While lumps can develop almost anywhere on a dog, paying attention to common locations can help identify potential cancers for further veterinary investigation. However, any new lump on a dog warrants monitoring and examination, even in less typical sites.


Cancerous lumps in dogs can vary greatly in size. According to research, smaller lumps under an inch may be less concerning, while larger lumps over an inch warrant closer monitoring and veterinary attention (Springhouse Animal Hospital).

Some of the most common cancerous lumps like mast cell tumors and lipomas often start small, ranging from the size of a pea to a walnut. However, any lump that is rapidly growing in size may be a sign of a cancerous tumor that requires veterinary assessment.

Larger lumps over an inch in diameter tend to be more concerning, as they may impede movement or functioning. Quickly enlarging lumps could also signify a fast-growing malignant tumor (Knutsford Vet Surgery). It’s recommended to monitor all lumps closely and report any significant size changes to a veterinarian immediately.


The shape of a cancerous lump can provide clues about its nature. Cancerous lumps often have an irregular shape compared to benign lumps. They may appear lobulated, with an uneven surface made up of small bumps or lobes.

According to Animal General CT, malignant melanomas often present as raised bumps that can be dark-pigmented with an irregular shape[1].

Cancerous lumps tend to have a more irregular, bumpy surface compared to benign fatty tumors like lipomas, which are typically smooth. The uneven, irregular shape occurs as cancer cells rapidly multiply in an uncontrolled way. A smooth, round, regular shape may indicate a benign lump like a lipoma or cyst.

So in summary, an irregular, lobulated shape with a bumpy surface can signify a cancerous lump, while a smooth, rounded, even shape may suggest a benign lump.

[1] https://www.animalgeneralct.com/site/blog/2021/07/27/lumps-and-bumps-on-your-dogs-skin


The firmness of a lump can help determine if it is cancerous or benign. A benign fatty tumor like a lipoma will typically feel soft and movable under the skin. As the Forever Vets article explains, a cancerous lump will often feel much harder and firmer than the surrounding tissue.

Cancerous lumps tend to feel hard and immovable, like a stone under the skin that is fixed in place. They do not move easily when pressed. As the Merck Veterinary Manual notes, malignant tumors often appear as firm, dome-shaped masses sticking out from the skin.

The firmness of a cancerous lump may fluctuate over time. It may start off feeling softer but become firmer and more defined as the tumor grows. Any lump that seems to be getting harder or changing in firmness over days or weeks warrants an immediate trip to the vet. Monitoring the lump for changes in firmness can help catch cancer early.


The mobility of a lump on a dog can be an important indicator of whether it may be cancerous. Cancerous lumps tend to feel firmly fixed in place, while benign fatty tumors called lipomas are more movable under the skin 1. A cancerous lump will generally become less mobile over time as it grows and invades surrounding tissues. Lipomas, on the other hand, tend to remain relatively movable unless they become quite large.

When first detecting a new lump on your dog, try gently moving the skin around it and see if you can move the lump itself. A lump that easily slides around under the skin is more likely to be benign. However, some malignant lumps may still be movable when they first develop. It’s important to monitor any new lumps for changes in mobility over the following days or weeks. If a lump becomes firmly fixed in place, this warrants a veterinary exam as it may indicate a cancerous tumor invading the tissues under the skin.

While mobility can provide some clues, it’s impossible to definitively diagnose a lump as benign or malignant at home. Any notable or suspicious lumps in dogs should be checked by a veterinarian, even if they seem movable at first. Your vet will examine the lump’s other characteristics and may recommend a biopsy to determine if it is cancerous.

Appearance of Cancerous Lumps

The appearance of a lump can provide clues as to whether it may be cancerous. Some signs to look out for in the appearance include:

  • Color – Cancerous lumps may have an abnormal color like red, blue, black or multi-colored. They can also appear bruised. A normal skin color is less concerning.
  • Ulceration – Lumps that ulcerate or open up can indicate cancer. This allows wounds and infections to develop.
  • Hair loss – Some cancerous lumps may cause hair loss and thinning around the area. This can help identify abnormalities.

It’s important to monitor lumps and note any changes in appearance. Rapid changes in size, shape, color or texture warrant an urgent vet visit. If the lump has an abnormal appearance, it’s best to get it evaluated by a vet as soon as possible.

Monitoring and Vet Visits

It is important to regularly monitor any lumps or bumps on your dog. Look for changes in the size, shape, color, or texture, as these could indicate cancer (https://www.westgatevet.com/site/blog/2023/03/15/bumps-dogs-skin-cancer). Track the lump’s growth rate by measuring it with calipers and recording the dimensions. Take photos to compare changes over time.

Have your vet examine any new or changing lumps as soon as possible, even if they appear benign. Your vet will assess factors like location, mobility, and feel to determine if a biopsy is recommended (https://www.anivive.com/learn/article/when-to-get-the-lumps-on-your-dog-checked-by-a-veterinarian). Early detection and diagnosis of cancer greatly improves treatment success and prognosis. Regular vet visits are key for monitoring existing tumors as well. Inform your vet about any changes, and follow their advice regarding rechecks and testing.


There are several common treatment options for cancerous lumps in dogs:

Surgery is often the primary treatment for operable tumors. The goal of surgery is to completely remove the tumor with clean margins around it 1. Surgery may not be possible for some inoperable tumors, but can become an option if chemotherapy or radiation therapy can shrink the tumor first.

Chemotherapy uses anti-cancer drugs to kill cancer cells and shrink tumors. It may be used before surgery to make a tumor operable, or after to help prevent recurrence 2. The specific drugs used depends on the type and location of cancer.

Radiation therapy uses high energy radiation to kill cancer cells and shrink tumors. It may be used alone or with surgery and/or chemotherapy. Side effects depend on the area being treated.

Palliative care focuses on managing pain and symptoms to improve quality of life. It may be used when a cure is not possible. Options include pain medication, nutritional support, and non-traditional treatments.

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