An Owners’ Practical Guide to Lumps on Dogs

Question: What could be worse than finding a lump on your dog?

Answer: Not finding the lump!

The important thing is you spotted the lump and are therefore empowered to act upon it.

Lumps on dogs are common and whilst many are not serious, some are. If you find a lump, be proactive and seek veterinary advice, because early diagnosis and treatment gives the dog a great chance of an uneventful recovery.

Nevertheless finding a lump is a heart-sinking moment. To help you better understand the implications, this practical guide covers:

Are All Lumps Cancer?

And now for the good news: Not all lumps in dogs are cancerous.  You found a bump, but this doesn’t mean your dog has cancer. There are other explanations such as:

  • Abscess: This is a localized pocket of infection, often the result of a bite that became infected.
  • Cysts: These are naturally occurring pockets of cheesy discharge, found within the skin. Think of them like a giant sterile spots.
  • Inflammatory reaction: A small area of skin becomes locally inflamed, typically after an insect or tick bite.
  • Skin tags: These are fleshy growth, commonly dangling from a stalk
  • Warts: Yep, dogs get warts.
  • Spots: Puppies are especially prone to acne-like spots on the belly or chin
  • Allergic reactions: Also known as urticaria, subtle bumps appear on the skin where the hair stands to give the coat a bumpy appearance
  • Ticks: A well-fed tick still attached to the host can mimic a dark, skin lump.

Checking for Lumps in Dogs

The golden rule is to find lumps early and then act.

Why Check for Lumps?

Should that lump be a cancer, removing it early often prevents spread. Check your dog regularly to spot new bumps and check existing ones for change.

What do you Do?

When checking for lumps in dogs, be methodical. Start at the nose and work down to their tail. In a short-coated dog a lump may be obvious, but less so in a hairy hound. The latter requires a fingertip search down to their skin to gently feel for any lumps and bumps under the skin.

Where do you Check?

Be sure to look in all those nooks and crannies, such as under ears flaps and the testicles. Other areas easily overlooked include armpits, between the toes, and under the tail. The latter is important in entire male dogs [£] as they are prone to perianal adenomas; and Cocker Spaniels [$] and their crosses who are over-represented when it comes to anal sac carcinoma

When do you Check?

A once weekly nose-to-tail check is advisable (or daily in tick hot spot areas! Remove these critters immediately to avoid tick-transmitted disease…but that’s another story.) Your fur-friend’s weekly grooming session is a great way to become familiar with their body to recognize what’s normal and what’s not.

However, a word of caution. Check existing lumps too often, such as every day, and it’s difficult to spot subtle changes in size or texture. But too long between checks isn’t great for obvious reasons. This is why once weekly checks work well, so you can spot change but in a timely manner.

5 Warning Signs of Worrisome Lumps

Your dog has existing lumps or pops up a new one, should you worry?

Maybe…or maybe not: Usually it’s not possible to make a diagnosis just by looking. However, certain clues can hint if an urgent exam is required or if it will wait until the dog’s next booster appointment.

When examining the lump, ask yourself the following questions:

Record what you See

If the lump shows even just one of these worrisome signs, then a vet check-up is advisable.

  • Photograph the lump or measure it and write down the measurements
  • Keep this info somewhere safe, and add to it each month. That way you’ll spot subtle changes in good time.

The Bigger Picture

Now look at the big picture. If your dog has a small lump that’s been quietly there for years, not causing problems, this is less worrying than a lump which is growing quickly, red, or the dog tries to chew. But when in doubt, have your vet check it out.

How are Skin Cancers Diagnosed?

Your dog has a lump. What can you expect from the vet visit?

vet looking for lumps under skin

The vet will ask general questions about the dog’s health and then the lump itself. Next comes a thorough physical examination. During this the vet checks the dog’s lymph nodes, to see if any are enlarged. They will also check the dog’s gums for signs of anaemia, listen to their chest, feel the abdomen, and also assess the actual lump.

This gives the vet a lot of information, but even then, it’s often not possible to make a diagnosis based on an exam alone. This is because some worrisome lumps can mimic harmless ones. Ideally, even harmless looking lumps should be analysed with a fine needle aspiration (FNA), just to be on the safe side

Fine Needle Aspiration

This involves the vet popping a fine needle into the lump and sucking back on a syringe. The idea is to flake off a few cells and harvest them in the needle hub. These are then puffed out onto a slide and looked at under the microscope.

For some lumps this gives a quick answer. However, this method does have drawbacks. Some lumps are so tightly knit that the cells don’t flake off and no sample is obtained. Another problem is that an accurate result relies on taking a representative sample of cells. For example, it can be like working out what flavor a cake is just tasting the icing.

But the good news is that many of the common harmless bumps, such as fatty lumps, give their cells away easily which makes a swift diagnosis possible.

If an FNA doesn’t give an answer or the vet’s suspicions are aroused, then a biopsy may be suggested. These take two forms:

Biopsy

Excisional Biopsy:  If the lump is small, then it may be simplest to remove the whole thing and send it away for analysis.

A Small Sample Biopsy: But if the lump is large or in a tricky place, then sending a small piece away can tell the vet if drastic surgery is necessary or not.

If the results come back suggesting something sinister, the vet may suggest additional tests such as a chest x-ray, abdominal scan, or FNA from the lymph nodes. This is called ‘staging’ and is used work out if the cancer has spread, which is important when deciding on treatment options.

Benign Vs Malignant

Two words the vet may use are ‘benign’ and ‘malignant’. These have big implications and it’s important to understand them

Benign lumps don’t spread to other parts of the body, and usually are more of a local nuisance than serious health threat. However, some types of benign lump can grow large and cause an issue due to size.

Malignant lumps seed off cells which travel to other parts of the body to cause new tumours in places distant to the original one. Common places for these ‘secondary’ tumours include the liver and lungs, but this varies depending on the type of cancer involved.

Treatment Options

The options vary depending on the size of the lump, its location, and whether it’s benign or malignant. Even a harmless fatty lump can cause problems if it grows in an inconvenient place, such as behind an elbow where it rubs with each step.

The Even Bigger Picture

But first, the vet should take into account the overall health and age of the dog. For example, an elderly dog with a slow growing fatty lump, may not need any treatment as it’s unlikely to impact the dog’s quality or length of life.

But should the same elderly dog have a large malignant tumour, then major surgery, intensive chemotherapy or radiotherapy may be required. This should trigger a frank discussion about the benefits of treatment and the dog’s welfare to decide what’s best for that individual. What’s appropriate for one patient, isn’t always what’s best for another.

Surgical Removal of the Lump

For a typical lump, surgical removal is recommended and often curative. Complete removal with a good margin of healthy tissue around it, is the end of the story for most dogs.

However, for large or aggressive lumps it can be tricky to remove enough tissue, especially if grows on a leg or the head, where there’s not much spare skin. In these cases, the surgeon will remove as much as possible (debulking surgery), but other therapies may be required such as radiotherapy..

checking nurse dog

Radiotherapy

Radiotherapy in dogs is used to treat highly aggressive tumours where complete removal is not possible.

Access to canine radiotherapy is limited to specialist centres [%]. The procedure involves repeated exposure to radiation over several sessions, each time under a general anaesthetic. The results can extend life expectancy, but there are practical drawbacks such as the distance to the nearest centre, repeated general anaesthetics, and the cost of treatment.

Chemotherapy

This involves giving drugs that are toxic to the rapidly dividing cancer cells. There are different protocols for different types of cancer. Some protocols can be given in first opinion practice or even at home, whereas as other are administered in specialist facilities.

The aim of chemo in dogs is to extend good quality life, rather than cure the patient. This means administering lower doses of medications, and so the side effects are less severe. This makes for a happier dog that can enjoy life whilst on treatment.

Less common therapies and those holding future promise include:

  • Metronomic Therapy: This involves giving a low dose of a chemotherapy agent regularly, to inhibit cancer growth. Some of these, such as Palladia [*] or Masitinib [@], are exciting options to treat potentially life-threatening conditions such as mast cells tumours.
  • Antiangiogenic Therapy: This involves drugs that inhibit the growth of blood vessels, starving the lump of nutrition. Drugs such as Palladia [*] have some antiangiogenic activity.
  • Cryosurgery: The surgeon applies liquid nitrogen to the lump, so that extreme cold kills the tumour cells. The lump dies and peels away 10 -14 days after treatment.
  • Photodynamic Therapy: This works best for thin, sheet-like skin cancers such as squamous cell carcinoma of the nose or ear tips. A special cream is applied to the area and activated by a special light source. This combination causes tissue death and the tumour to flake away
  • Immunotherapy: Working on a similar principle to vaccination, immunotherapy involves giving doses of antigens which stimulate the immune system to produce anti-cancer antibodies. [#]

Dog Skin Cancer: Breed-related Risks

Lumps on dogs become more likely as the pet ages. But do you know other factors increase the risk, such as the dog’s breed?

Some dog breeds are at a greater risk of developing specific cancers than others. Owners of these breeds should be extra vigilant for new lumps on dogs.

  • Bassett Hound  –  Squamous cell carcinoma, anal adenoma
  • Bernese Mountain Dogs  –  Mast cell tumours, histiocytoma
  • Bloodhounds –  Squamous cell carcinoma
  • Boston Terriers  –  Mast cell tumours, histiocytoma
  • Boxers  –  Mast cell tumours, histiocytoma
  • Bulldogs –  Histiocytoma
  • Chinese Shar Pei –  Histiocytoma
  • Cocker Spaniels – Anal sac adenocarcinoma
  • Dachshunds      –   sebaceous adenoma, melanoma
  • Greyhounds –  Histiocytoma
  • Golden Retrievers –  Mast cell tumours, melanoma
  • Labradors –  Lipomas, mast cell tumours
  • Pugs –  Mast cell tumours
  • Rhodesian Ridgebacks –  Mast cell tumours
  • Schnauzers  (miniature and standard)  –  Malignant melanoma
  • Scottish Terriers  –  Malignant melanoma, histiocytoma
  • Poodles  –  Squamous cell carcinoma, sebaceous adenoma
  • Staffordshire Bull Terriers  –  Mast cell tumours

Common Lumps on Dogs

As the saying goes: “Common things are common.”: What does this mean when applied to dog skin cancer?

Lipoma

Lipomas are also known as ‘fatty lumps’. They consist of a pad of fat that grows slowly to produce a soft, round lump. These lumps are extremely common, in older dogs especially if overweight.

A lipoma can be diagnosed by a simple FNA test. If the lump is not causing a physical problem, such as getting in the way of a leg, then they can be left alone.

Very rarely, a more serious fatty tumour, a liposarcoma, can develop. These are similar to a lipoma but feel harder and grow rapidly. These are a malignant cancer and should be removed where possible.

Histiocytoma

At the other end of the age scale, histiocytomas are more common in young dogs, under two years of age. They grow on the skin and have a raised button-like appearance. The surface can ulcerate, giving them an angry appearance.

Histiocytomas are benign, and after a few months may go away of their own accord. The problem is to tell them apart from a mast cell tumour, which is potentially much more serious and should be removed. Therefore it is sensible to remove suspicious lumps and confirm the diagnosis on histology.

Mast Cell Tumours

Mast cell tumours are a serious dog skin cancer with the potential to spread and be life-threatening. Unfortunately mast cell tumours can look like other less worrying lumps, causing complacency and missing a vital opportunity for early treatment.

Mast cell tumours may look like an innocuous firm skin nodule, or may be red and itchy. The most serious ones can also cause general illness such as vomiting. Owners of at-risk breeds (Boxers, Boston Terriers, Staffies, and Golden Retrievers) should therefore take any new lump seriously and visit the vet.

Mammary Carcinoma

Female dogs, especially those that are not neutered, can develop breast cancer, of which mammary carcinoma is one type. In entire female dogs, around one-in-four will develop some form of breast cancer. Happily, many of these lumps are benign, but even so a vigilant owner and early removal of suspicious lumps  are advised to reduce the risk of spread. Radical surgery is sometimes required, such as removing all the mammary tissue on the side where the lump is found. Better still, when a female dog is spayed before or first or second season, this has a huge protective effect that greatly reduces the risk of her developing breast cancer later in life.

Melanoma

Melanomas are pigmented skin lumps on dogs that behave slightly differently to human melanoma. In dogs, many melanomas are benign, meaning they aren’t aggressive and don’t spread. However, a few are highly malignant and therefore no melanoma should be ignored.

Characteristic of malignant melanomas is their dark appearance (although, atypical non-pigmented melanomas can confuse the picture), rapid growth, and presence in the mouth or on a limb. Unfortunately, these lumps are often in locations that makes removal difficult, and additional therapies such as radiotherapy may be required.

Sebaceous Adenoma

Common in middle-aged and old dogs, a sebaceous adenoma looks much like a wart. They can be several centimetres across and look like pink, fleshy lumps. They are the result of a proliferative growth of the skin’s sebaceous glands.

These lumps are harmless and of cosmetic concern only. However, they can sometimes become damaged if caught by a brush or the collar, and require removal to stop them causing discomfort.

Perianal Adenoma

Similar to a sebaceous adenoma, these are skin growths located around the anal area in male dogs.  These lumps are fed by the male hormone, testosterone, and are common in older, entire male dogs.

Whilst the growths themselves are benign, sometimes they can grow quite large and then ulcerate. This is undesirable because of the risk of infection from faeces, and also they can bleed profusely.

Surgical resection or cryotherapy is advisable, along with desexing to remove the source of hormone which would feed new lumps.

Anal Sac Adenocarcinoma

This cancer affects the anal sacs and once the tumour reaches a certain size, can bulge out through the skin. These are aggressive, malignant cancers and so early detection, with removal of the anal sacs is the treatment of choice.

Squamous Cell Carcinoma

Squamous cell carcinoma is a form of dog skin cancer induced by exposure to UV light. In the early stages it causes flaky redness, which eats into the skin and becomes ulcerative as the condition worsens.

Along with preventative treatment, such as avoiding the sun and applying sunblock, surgery or photodynamic therapy is indicated.

Be Proactive about Lumps on Dogs

If you take one thing away from this article, it’s that early detection of lumps on dogs is their best chance of making a recovery.  Happily, not all lumps and bumps are cancer, but the wise pet parent gets any new lumps checked by a vet. If the news is good you have peace of mind, if things are more serious then early action can often prevent worrying complications.

References

[£]Perianal adenocarcinoma in the canine male – a retrospective study of 41 cases. JAAHA 26 (3), 329-334.

[$]Ross J T, Scavelli T D, Matthiesen D T & Patnaik A K (1991) Adenocarcinoma of the Apocrine Glands of the Anal Sac in Dogs: A Review of 32 cases. J Am Anim Hosp Assoc 27 (3), 349-355.

[%] SASH Vets, Sydney    & South Paws, Moorabin

[&} Antiangiogenic therapy Cancer Research UK

[*] Palladia FAQ , Zoetis

[@] Masitinib is Safe and Effective for the Treatment of Canine Mast Cell  Tumours. JSAP

[#] Immunotherapy works for dogs too. Cancer Research