11 Common Dog Lumps, Bumps, Tumors and Cysts (with Pictures)

✔️Article written by a veterinarian & reviewed by Dr. Whittenburg, director, on Dec 15th 2022. View our editorial quality process.

In this article, we will review pictures and information about common lumps and bumps that may appear on a dog, including lipomas, warts, cysts, skin tags, tumors and cancerous lesions. Some may be benign and nothing to worry about. Others may be cancerous and require immediate veterinary attention.

Note that it is always advisable to have any lump, especially an old dog lump, biopsied to make sure that it is benign and not anything more sinister. Needle aspiration is a very quick and simple process, or a punch biopsy is also straightforward and often only requires a local anesthetic. Either will give you peace of mind. Let’s review now pictures and information about the most common lumps and bumps in dogs.

Common Types of Lumps and Bumps on Dogs (With Pictures)

It can be difficult to tell the difference between a benign and a more serious, potentially cancerous tumor or growth. Any new (or growing/changing) lump always needs to be examined by your veterinarian. We will start with lumps and bumps that are common in senior dogs, but any dog, at any age, can develop the lumps discussed on this page.

1. Lipomas on Dogs

Lipomas are the most common benign (ie NON-cancerous) growth seen in dogs. Each lipoma is made up of a group of fat cells that forms a soft round, or oval, lump usually located just below your dog’s skin.

Lipomas are generally easy to move around and don’t feel as though they are connected to deeper tissue in the body. They are usually slow growing. Sometimes they will stop growing, but don’t often disappear or get smaller. Although these common old dog lumps are not dangerous in themselves, larger lipomas can cause discomfort. Depending on where they are located, lipomas can cause difficulty with movement, or even put pressure on internal organs.

Although many veterinarians consider these fatty lumps a normal part of the aging process in dogs, they can also be a sign of certain health conditions. Dogs who are overweight are more prone to developing lipomas. Dogs with hypothyroidism and other metabolic problems are also at an above-average risk of having lipomas.

How to treat lipomas on dogs: Veterinary opinion on the best way to deal with lipomas is varied, and your vet will likely have their own take on this. For verified lipomas, the choice is either to leave them be, or to have them surgically removed. Some lipomas that are left to their own devices will stay the same size; others will keep growing. The decision of whether to remove one or not depends on its location, size, and whether or not it is affecting your dog negatively. Learn more about Lipomas in Dogs: What They Look Like [With Pics] and What to Do.

2. Dog Warts

Warts (also called papillomas) are the other most common type of old dog lumps and can occur on your dog’s skin, on his eyelids, paw pads, between the toes, around the genital area, or in their mouth.

They can show up as a single small lump, or as a group or cluster of tiny lumps which look a little bit like a cauliflower floret. Older dogs tend to develop single warts, whereas puppies are more prone to multiple wart groupings. However, either type of papillomas/warts can develop on a dog of any age.

Warts on dogs are most often benign and will often disappear of their own accord after a few months. Occasionally they can be, or become, cancerous so any wart that is a long-term issue, or that changes in color/size/look needs to be investigated by a vet.

Treating warts on dogs: Simple old dog lumps like benign warts usually don’t need any treatment unless they get infected, get in the way, or become irritated. This can happen if a dog licks or scratches at the wart, or it is in an area that’s rubbed by a collar or harness, for example. Learn more: Dog Warts: What They Look Like & What to Do.

3. Sebaceous Cysts on Dogs

Sebaceous cysts are not predominantly old dog lumps. They’re common in dogs of all ages and can occur singly, or your dog could have several of them.

These types of dog cysts can be tiny or grow up to an inch or more in size. They tend to resemble a human ‘pimple,’ just larger.

Causes of dog sebaceous cysts: A sebaceous cyst forms when a pore or hair follicle in your dog’s skin becomes blocked or clogged. Matter (oil, skin cells, dirt, and such) collects behind the blocked pore and forms the cyst just below the skin. As always, it can be difficult to tell the difference between all the different types of old dog lumps you might find… always have your vet take a look and make the diagnosis.

Treating sebaceous cysts in dogs: Sebaceous cysts are benign and generally don’t need any treatment as they resolve on their own in one of three ways: ‘Come to a head’ and burst or ooze out the pus/gunk inside. This may be disturbing to owners, but it’s important to keep the area clean and dry to prevent infection. Learn more: Sebaceous Cysts in Dogs, and 6 Types of Dog Cysts [With Pictures].

4. Skin Tags

A skin tag is a benign growth that develops on the surface of your dog’s skin. They vary in appearance with a range of different sizes and shapes. Many skin tags are pedunculated – this means that they are attached to the skin via a narrow stalk leaving them dangling in space.

Skin tags are non-cancerous and generally don’t cause any harm to your dog. However, skin tags often develop on areas of your dog’s skin where there is high friction, such as areas that are in contact with the ground or their collar. Over time, constant rubbing of these skin tags will lead to irritation and may be painful for your dog. In the majority of cases, skin tags are not anything to worry about, but if you have any concerns, have your veterinarian test your dog’s lumps. Learn more about skin tags (with pictures)

5. Histiocytomas

A histiocytoma is a benign (non-cancerous) growth found on the skin of young dogs. These growths form when a type of immune cell in your dog’s skin over-replicates. The over-replication causes tissue build-up and inflammation (histiocytoma). While they occur commonly in dogs under three years old, they can affect any dog. Most histiocytomas will heal without treatment in 2-3 months. However, in some cases, they can get worse with time. They can look pretty scary to the untrained eye, and it can be hard to tell them apart from dangerous growths in dogs. Learn more about histiocytomas and view more pictures.

Cancerous Tumors, Bumps or Lumps in Dogs

Although most dog lumps and bumps are benign, cancerous tumors can develop, and it’s often difficult to tell the difference between a benign or a malignant (cancerous) growth. ANY new lump, bump, growth, or cyst needs to be examined by your veterinarian so that he can diagnose it properly. Cancerous, or malignant, tumors of the skin can be small or large. They may itch or cause the senior dog some discomfort. They may do neither.

Cancerous skin lumps or tumors in dogs include mast cell tumors, mammary gland tumors, malignant melanoma, and squamous cell carcinoma. Let’s look at pictures, starting with mast cell tumors.

6. Mast Cell Tumors

In healthy dogs, mast cells are the part of the immune system that releases histamine in response to allergies. Mast cell tumors are more often seen in middle-aged and older dogs but can affect younger dogs too. These old dog lumps are very commonly both malignant and aggressive, but it’s impossible to know which ones are and which aren’t without a biopsy.

Image by Joel Mills (Own work) GFDL CC-BY-SA-3.0,
via Wikimedia Commons

Mast cell tumors can vary a LOT in appearance; usually, they’re a fairly smooth, round growth visible on the skin. Other times they can look like a wart, or resemble a lipoma, and sometimes they are red in color.

Mast cell tumors are more common in these breeds:

• Beagle
• Boxer
• Boston Terrier
• Bulldog
• Bull Mastiff
• German Shorthaired Pointer
• Golden Retriever
• Great Dane
• Labrador Retriever
• Pug
• Rhodesian Ridgeback
• Scottish Terrier
• Shar Pei
• Staffordshire Bull Terrier
• Weimaraner

Learn more in our article about “Mast Cell Tumors: a Veterinarian’s Guide for the Dog Owner“.

7. Melanoma

Melanoma tumors are dark and can be small, large, flat, or raised. They can be either benign or malignant, so they shouldn’t be ignored. Below is a picture of a melanoma inside a dog’s mouth (black growth):

If a dog has malignant melanoma, it’s usually an aggressive cancer that spreads throughout the body quickly, so the lesion needs to be surgically removed as quickly as possible. Only a veterinarian can tell the difference between a benign and a malignant melanoma by doing a biopsy.

Most malignant melanomas in dogs grow in/around the mouth or in other mucus membranes, but they can also be found in other areas. Melanomas are more common in:

• Anatolian Shepherd
• Cocker Spaniel
• Chow Chow
• Dachshund
• Golden Retriever
• Gordon Setter
• Poodle
• Scottish Terrier

8. Squamous Cell Carcinoma

Squamous cell carcinomas in dogs are fairly rare, and they are not as aggressive in terms of spreading as melanoma or mast cell tumors are.

These types of malignant tumors are usually found on areas of skin that are bare, or have little hair, and are more common in dogs with light-colored skin. Squamous cell tumors in dogs can be raised lumps or nodules, or flatter areas of ulcerated skin. They can sometimes resemble warts.

Squamous cell tumors are more common in:

• Basset Hound
• Beagle
• Bull Terrier
• Collies
• Keeshonds
• Schnauzers (standard)

9. Mammary Gland Tumors

Dog mammary tumors are lumps that come from the mammary tissue along a dog’s belly. Not only are dogs capable of developing breast or mammary cancer, but they do so at an alarming rate, especially if they’re left intact. An intact female has around a 23-34% chance of developing a mammary tumor during her lifetime. Mammary tumors in dogs are benign about half the time and malignant about half the time.

Benign mammary tumors in dogs are usually small, firm, and well-defined. You may notice a small lump while petting your dog’s belly, as showcased in our picture below:

Malignant mammary tumors may be small, large, or a single lump, or multiple lumps. They often have bumpy edges and are tightly fixed to the skin or underlying tissue. Read more: Mammary Tumors in Dogs.

10. Sarcoma Tumors

Hemangiosarcoma is a malignant cancer of the cells that line the blood vessels of the body. Therefore, hemangiosarcoma can occur anywhere in the body where blood vessels are found. In the case of hemangiosarcoma, the cells that line the blood vessels start dividing uncontrollably and in an unhealthy manner. This leads to the development of a mass that is very prone to rupture and can even cause a dog to bleed out internally. Read more: Hemangiosarcoma in Dogs: A Vet Explains.

11. Anal Gland Tumors

Anal gland tumors are usually cancerous. You will notice a growth located next to the dog’s anus, as shown in the picture below.

Not Finding What You Want?

Check out our other pages about skin conditions in dogs:

Red Bumps and Lumps on Dogs

21 Common Dog Skin Conditions

Skin Lesions, Bumps, and Lumps Due to Cancer

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How Do You Know When a Skin Lesion or Lump Is Cancerous?

Cancer is the abnormal and rapid growth of previously healthy cells. Therefore, lesions or lumps that are growing rapidly or changing in appearance quickly may indicate a more sinister underlying cause.

Ulceration, redness, and a firm texture are all common properties of a cancerous lesion, but that doesn’t mean that every lump with these features will be cancerous.

Cancerous, or malignant, skin lesions and tumors can be small or large. They may itch or cause the senior dog some discomfort. They may do neither.

You can never say whether a lesion is cancerous just by looking at it, but there are some clues that can help raise suspicions:

• Rate of growth: Cancerous lesions tend to grow and spread more rapidly than those that are benign. They will grow into the surrounding healthy tissue, causing damage and inflammation. If a lesion doubles in size over the course of a few weeks, then it’s best to get it checked.
• Texture: Cancerous lesions and lumps are often harder and firmer to the touch.
• Shape: Due to their rapid and erratic growth, cancerous lumps tend to appear more irregular in shape.
• Color: Red, black, or just generally ‘unhealthy’ looking lesions may be more malignant in origin.
• Discharge: Oozing or discharge from the lesion may occur due to damage and death of the tissue in surrounding areas. While any lump can develop a secondary infection, sinister lumps are more prone to producing pus and bleeding.
• Irritation: A lump that is itchy or causing discomfort to your dog is more likely to be cancerous.

Skin cancer is more common in older dogs also, and a dog’s skin will naturally change with age so sometimes it can be hard to tell whether changes are due to simple old age or due to a more sinister underlying cause. Therefore, it’s important that your vet has a proper look to make the diagnosis – it’s a good idea to have any new lump or bump tested by your veterinarian.

Overview: Pictures of 9 Common Dog Lumps, Tumors, Warts, and Cysts

Click here to see a list of pictures of lumps, tumors, cysts, or warts that are often observed on dogs as they get older.  Pictures are provided as examples only, as it is usually not possible to determine the true nature of a lump without testing and analysis.

Treating Malignant Skin Tumors in Dogs

The best way to treat most malignant or cancerous lumps in dogs is to remove them surgically, and as quickly as possible. The smaller the lump the easier the surgery and the less tissue which must be removed. There are also newer injectable treatments for mast cell tumors as well as vaccines to prevent the recurrence of malignant melanoma. Acting fast helps to reduce the chances of the cancerous cells metastasizing (traveling) into other tissues, organs, and lymph nodes. Sometimes radiation therapy, chemotherapy, or other treatments are recommended in addition to removing the tumor.

The exact treatment options will be decided by your veterinarian who will consider the size and location of the tumor and whether it has spread to other areas of the body.