Simple, accurate health tests for the home and the workplace.

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 they are benign lumps 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). A lump or growth can, however, be a malignant tumour requiring immediate treatment. It is, therefore, essential to get any suspicious changes in the 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 is the difference between a cancerous and a non-cancerous lump?

Although a lump is most likely to be benign, it is natural to fear something more serious.  Growths such as cysts, blisters, warts, abscesses, hematomas, skin tags or pimples are more likely to be benign but if not examined and assessed by your vet early on, can go on to develop into something more troublesome to your pet.

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 parts of the body (metastasize).

What are the causes of lumps, growths and skin masses on dogs?

Skin masses can be caused by many different things including infection, blocked hair follicle (sebaceous cyst) or enlarged oil gland in the skin (sebaceous adenomas) and cancer. Some of the most common causes are:

Hematoma – 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 usually quite small but can become large and irritable to your pet.

Abscess – usually caused by a bacterial infection at the site of a bite or puncture wound.

Histiocytoma – these are fast growing dome shaped masses which can be found anywhere on a dog’s body.  This type of mass is more commonly found in younger dogs.

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

Papilloma – caused by viruses and appear as warts on eye lids, 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.

Lymphoma – 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.

Melanoma – brown or pink bumps usually found 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 risk factors of a dog developing a skin mass?

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 considered at greater risk of developing some skin masses such as sebaceous adenomas, Basal cell tumour and papillomas.  Histiocytoma and Lipoma are more commonly seen in Labradors, retrievers, Dobermans and Dachshunds. Other breeds considered more likely to suffer with skin tumours include Boxers, Scottish Terriers, Bullmastiffs, Bassett Hounds, Norwegian Elkhounds and Weimaraners.


The vet will ask a number of questions regarding the appearance of the lump such as when it first appeared, any change in size or shape and whether it is causing your dog any irritation or distress.  The vet will undertake a physical examination and will probably advise to taking either an impression smear or a needle biopsy of the lump.  The needle biopsy (fine-needle aspirate) will involve 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 are effective, then your vet is likely to recommend a tissue biopsy.  This will necessitate your pet being sedated, either with a local or general anaesthetic depending on the size and location of the lump and whether the vet feels he needs take a sample or remove the lump completely. It will be necessary for some of the non-affected area around the lump to also be removed with the sample for analysis.

What treatment is there for growths, skin masses and tumours?

Treatment very much depends 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 pet any discomfort, the vet is likely to advise that it is not removed but for you to look out for any change in size or texture of the lump and to have to 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 effected cells have been removed.  X-rays may be recommended to check whether the cancer has spread to other parts of the body, followed by radiation and/or chemotherapy if required.  Treatment will also involve taking blood tests to look at your dog’s response to treatment and overall health.

All treatments will need to 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 and so should not be kept out in the sun for long periods.  Generally, there is no certain way of avoiding most skin growths or tumours. 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 easier and increases the chances of a favourable outcome.