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Lumps, growths, tumours and skin masses on Dogs

What Is a Skin Mass?

Skin masses are very common in dogs. They can be found on the skin (Cutaneous Tumours) or under the skin (Subcutaneous Tumours). In the majority of cases, lumps found on dogs are benign, caused by a fatty mass under the skin (Lipomas), a blocked hair follicle (Sebaceous Cyst) or an enlarged oil gland in the skin (Sebaceous Adenomas). However, a dog’s lump or growth could be a malignant tumour requiring immediate treatment. It is, therefore, essential to get any suspicious changes in a dog’s skin checked out so that your vet can assess whether the mass is benign, needs to be removed or is a danger to your dog’s health.


What Causes Tumours/Lumps In Dogs?

Skin masses can be caused by many different things, including infection, a blocked hair follicle (Sebaceous Cyst) or enlarged oil gland in the skin (sebaceous adenomas) and Cancer. 

There are various types of lumps/tumours that can develop in dogs, so it is impossible to narrow down the causes. Generally speaking, the cause of lumps in dogs is an abnormal growth of cells in a dog’s skin or tissue. But, the root causes are a lot more complicated than this.

Here are some of the most common causes of growths in dogs:

  • Age – the chance of a dog developing cancer increases with age
  • Hormonal Imbalance – this could either be down to genetics, drugs, or pregnancy
  • Diet – an unhealthy or carb-heavy diet can encourage tumour growth
  • Weight – being overweight means a higher chance of dogs developing tumours
  • Sun Exposure – dogs with fair/no fur develop skin cancer more often, along with working dogs who spend longer outdoors
  • Breed – certain breeds are more prone to tumours than other breeds
  • Week Immune System – dogs with weakened immune systems are more likely to develop serious tumours/growths


What Is The Difference Between a Cancerous and a Non-Cancerous Lump?

Although lumps found in dogs are most likely to be benign, it is natural to fear something more serious. The following lumps are most likely to be benign:

  • Cysts
  • Blisters
  • Warts
  • Abscesses
  • Hematomas
  • Skin Tags
  • Pimples 

But, if the lumps listed above are not examined and assessed by a vet early on, they could develop into something more troublesome for your dog.

Cancerous growths can be either malignant or benign. If a lump is benign, it tends to only appear in one place and not spread to other parts of the body, although it can become very large. Malignant growths tend to spread quickly and to other body parts (Metastasize).


Are Cancerous Lumps on Dogs Soft or Hard?

The ultimate advice is to take your dog to the vet. It is always best to have your pet assessed by a professional. However, we want to advise what you should look out for. Benign lumps often feel fatty and soft to the touch – however, a cancerous tumour is usually harder and firmer. A hard, immovable lump on your dog is a sign that you must book an appointment at the vet as soon as possible.

If your dog is also suffering from any of the following symptoms, then it’s time to call the vet:

  • The sudden appearance of lumps
  • Changes in size, colour, or texture
  • Discharge from lumps
  • Discharge from the nose or eyes
  • Significant weight loss
  • Chronic Vomiting or Diarrhoea
  • Lethargy and weakness
  • Wounds that aren’t healing


What Are The Different Types of Tumours In Dogs?


These are sacs or blisters filled with blood, usually found on a dog’s ear flaps.

Skin Tags

Benign skin growths that protrude from the skin. They are generally relatively small but can become large and irritable to your dog.


Usually caused by a bacterial infection at the site of a bite or puncture wound.


These are fastgrowing domeshaped masses found anywhere on a dog’s body. This type of mass is more commonly found in younger dogs.


These are benign fatty skin masses usually found along the dog’s rib cage, particularly in older dogs.


These are caused by viruses and appear as warts on eyelids, genital region, lips, tongue and muzzle. These warts can ulcerate, causing your pet discomfort and can develop into Squamous Cell Carcinoma (see below).

Basal Cell Tumour

Appears as a round, hairless nodule in the skin and is usually located on the dog’s head, neck, or shoulders.


Is a cancer of the lymphatic system. The lymph nodes become inflamed, causing them to become large and lumpy, giving the appearance of a skin mass. The skin form of lymphoma causes round, raised nodules.


Brown or pink bumps usually found in/around a dog’s mouth, eyes or dark areas of skin and can be malignant.

Squamous Cell Carcinoma

These tumours are usually found on a dog’s belly, scrotum, legs, feet or muzzle and have a red or grey, bumpy appearance. This is a malignant type of skin cancer.


What Are The Risks Associated With Lumps In Dogs?

Dogs who are exposed to sunlight for prolonged periods are at an increased risk of developing skin tumours, particularly hairless dogs and those with white coats. 

Genetics is considered a contributing factor. For example, Cocker spaniels and poodles are at greater risk of developing skin masses such as Sebaceous Adenomas, Basal Cell Tumours and Papillomas.  

Histiocytoma and Lipoma are more commonly seen in Labradors, Retrievers, Dobermans and Dachshunds. Other breeds considered more likely to suffer from skin tumours include Boxers, Scottish Terriers, Bullmastiffs, Bassett Hounds, Norwegian Elkhounds, and Weimaraners.


Professional Diagnosis of Lumps/Tumours in Dogs

The vet will ask several questions regarding the appearance of the lump, such as:

  • When it first appeared, 
  • Any change in size 
  • Any change in shape
  • Whether it is causing your dog any irritation
  • Whether it’s causing your dog any distress

The vet will undertake a physical examination of the lump and will probably advise taking either an impression smear or a needle biopsy of the lump.  


The needle biopsy (fine-needle aspirate)

Involves inserting a needle into the lump and drawing cells from the lump using a syringe. These cells are then placed on a glass slide to be examined under a microscope.  

An impression smear

Involves pressing a glass microscope slide against the surface of the mass to collect skin cells which can then be analysed. 

If neither of these options is effective, then your vet is likely to recommend a tissue biopsy. It will be required for your dog to be sedated during this process. This will either be with a local or general anaesthetic, depending on the size and location of the lump. The decision also depends on whether a sample is taken or the lump is removed completely. It will be necessary for some of the non-affected areas around the lump to also be removed with the sample for analysis.


What Treatment Is Available for Growths, Skin Masses and Tumours In Dogs?

Treatment depends very much on the results from the cell analysis. Where a cyst or abscess is found to be benign, your vet is likely to lance and drain it and, in the case of an abscess, follow treatment with a course of antibiotics.

If the lump is found to be a benign fatty mass and not causing your dog any discomfort, the vet will likely advise that it is not removed. Alternatively, they may advise you to look out for any change in size or texture of the lump and to have regular check-ups.

If the mass is malignant, you will, in most cases, be advised to have the lump removed together with the area surrounding the mass. This will be sent off to a pathology lab to be examined to ensure all affected cells have been removed. X-rays may be recommended to check whether the Cancer has spread to other body parts, followed by radiation and/or chemotherapy if required. Treatment will also involve taking blood tests to determine your dog’s response to treatment and overall health.

All treatments must be followed up with regular check-ups for any reoccurrence.


How Can Growths, Skin Masses and Tumours be Prevented?

As previously mentioned, hairless dogs and those with white coats are at an increased risk of developing skin tumours, so they should never be kept in the sun for long periods. 

Generally, there is no certain way of avoiding most skin growths or tumours in dogs. The best precaution is to check your dog regularly for any lumps, bumps and changes in skin colour and texture. Then, if you notice anything that causes concern, book an appointment to see your vet. 

Early treatment is often more straightforward and increases the chances of a favourable outcome.


Further Help and Advice

If you’re worried about your dog’s lumps/growths, or any related symptoms, speak to a vet to rule out anything serious and receive guidance on how to ease the symptoms.

In the meantime, you can find more information on pet health in our handy guides. Plus, browse our range of dog health tests suitable for home use. You can carry out these tests in the comfort of your own home, receiving fast, accurate results to help you rule out certain illnesses.