What can turn an affectionate pat or cuddle with your dog into an anxious moment? Finding a lump! Understandably the first thing that often springs to mind is that it could be cancer, however not all bumps and lumps on dogs are cancerous tumours. Sometimes they’re relatively harmless, such as sebaceous cysts which can occur as a result of blocked oil glands, or lipomas which can be unsightly but are harmless. Skin growths are common in dogs and fortunately many of them tend to be benign.


Sebaceous cysts

The sebaceous glands secrete an oily liquid which helps to keep dogs’ coats shiny and healthy, and brushing your dog helps to stimulate the glands so that they release the oil. Brushing also helps to keep these glands functioning efficiently and prevent cysts, however blockage of a follicle or pore can cause the build-up of oil and lead to the formation of one. Commonly, the first time dog owners become aware of sebaceous glands is when they become blocked and cause a cyst.


Cysts can develop from sweat or dead cells and they normally grow to a certain size before rupturing and subsequently healing, thereby needing no other treatment. Some become infected and need to be removed, but pathology tests should be conducted first in these cases. Certain breeds are more susceptible to sebaceous cysts, such as Cocker Spaniels.


Sebaceous cysts may not bother your dog, and some actually stop growing and neither shrink nor rupture, but they should be checked by a vet regardless. Sebaceous glands sometimes develop into tumours called sebaceous adenomas but they rarely create ongoing problems after being surgically removed.



Another commonly occurring lump in dogs is the lipoma. They are rounded, soft masses which are painless, and are usually found just under the skin.  They are usually benign, and after reaching a certain size simply remain in place and cause no problems. Another type of benign lipoma are infiltrative lipomas. These occur in the connective tissues deep between muscles and sometimes need to be removed.


Most lipomas do not cause pets discomfort unless they grow large and affect movement in places such as under the front leg. They can appear anywhere but are often found on dogs’ trunks or bellies. Most dogs with a lipoma will develop several eventually. They often occur in middle-aged or on older dogs and are considered a natural part of aging. Any breed can get them, but overweight and larger dogs are more prone.


Most vets take a precautionary approach to lipomas when they’re in a sensitive place or growing quickly, by removing them. There is an invasive version called an infiltrative lipoma, and these can appear reddened and irritated. If these rapidly growing masses are detected in places such as on the gums, prompt action is required to treat and/or remove them.



Other types of non-cancerous lumps include warts, hematomas (blood blisters) and abscesses.  Most do not cause concern and are of no discomfort to the dog. Warts are caused by a virus and can occur around the mouths of young dogs. They usually go away by themselves but older dogs might need surgery to remove them.  Abscesses occur as a result of a build-up of pus under the skin. Bites from insects and other animals or infection can cause them.


Cancerous lumps

Growths can sometimes be cancerous of course, and cancerous growths can be either benign or malignant. Malignant growths tend to spread quickly and can metastasize to other areas of the body. Benign growths tend to remain where they originated and do not metastasize, but they can grow into large tumours.


Tumours that need immediate attention by a vet include mast cell tumours, mammary gland tumours, malignant melanoma, cutaneous lymphosarcoma, and fibrosarcoma.  Mast cell tumours are the most commonly occurring skin cancer in dogs and are often found in Labradors, Terriers, Beagles, Boxers, Schnauzers and Shar Peis, but can occur in all breeds.


Can something harmless become malignant?

Sebaceous adenoma can sometimes turn into sebaceous adenocarcinoma, which are malignant. If the tumour starts growing rapidly and its surface is ulcerated you should suspect malignancy, but they are sometimes mistakenly assumed by dog owners to be warts. Usually no intervention is necessary provided there is no bleeding or ulceration, they’re not growing quickly, and they’re not in an area that can cause other problems or where the dog can scratch them and make them bleed.


How can you tell which lumps are dangerous and which to leave alone?

There are a number of techniques your vet might use to diagnose the composition of a lump. Impression Smears involves pressing a glass microscope slide against the raw surface of the lump. If the vet cannot make a diagnosis from the smear they’ll refer it to a veterinary pathologist.


Many lumps can be analysed via a needle biopsy which is done by inserting a sterile needle into the lump and extracting some cells from the lump. The cells undergo pathological examination and a total excision of the lump is conducted if removal is required.


Analysis of internal organs usually requires ultrasound. Ultrasound scans can be helpful in determining if metastasis of a malignant tumour to deeper areas of the body has occurred. X-rays are also used for collecting evidence of internal masses. CT or MRI scans may be necessary in some cases. The most accurate way to determine whether lumps are dangerous is to have them assessed by a pathologist, and this might be recommended by your vet.


Caution needs to be exercised with all lumps and bumps on dogs because what will happen to them cannot be predicted with certainty.  Keeping a close eye on them is essential so that they can be removed at the first sign of trouble.



Each case needs to be evaluated according to its own circumstances, and your vet will recommend treatment based on a number factors including the dog’s age and general health. An important standard approach to eliminate nuisance or dangerous lumps is to surgically excise them.


Sometimes chemotherapy is recommended as the chemicals used are highly toxic to rapidly dividing cells making it a mode of treatment for fast growing tumours. Sometimes a combination of surgery and radiation/chemotherapy can help in achieving a cure. Chemotherapy is often used as a precautionary procedure after a lump has been surgically removed.

Radiation can be effective with invasive tumours that spread rapidly and that do not have well defined borders. Radiation therapy is appropriate for certain types of tumours and is often used in addition to surgical excision.


Keeping an eye on things

Bear in mind that not all lumps and bumps are cancerous, and many are fatty tumours and consequently do not require immediate surgery. Some look quite innocent when in fact they’re not, which is why you can’t afford to gamble with your dog's health and it’s important to get any lumps and bumps checked. Fast growth, redness, pus, swelling, an opening in the lump, and pain, are reasons to seek immediate veterinary attention.


When taking your dog to get lumps checked your vet will mostly likely ask whether the lump appeared suddenly, whether its shape, colour or size has changed, and whether your dog’s behaviour, such as his appetite or energy level, is different. Once diagnosed, your vet might record the location and sizes of lumps and bumps that aren’t removed to make it easier to keep track of what’s changed and any that are new in future. This is something that dog owners can do too, and an ideal time to check is when brushing, bathing, or petting. Doing it regularly will help you increase your familiarity with your dog’s body so that you’ll detect a change more quickly. 


Even if your dog has a lump that you find is not cancerous, always have new ones tested and keep a close eye on all of them. Any of the Vets4Pets hospitals can help with examination and diagnosis of lumps and bumps. The sooner you have them checked, the sooner your dog can receive treatment if they’re problematic, and if they’re not, the sooner you’ll have peace of mind.