11 Common Dog Lumps, Bumps, and Growths (with Pictures)

This article was updated on October 3rd, 2023

In this article, we will review pictures and information about common lumps, bumps or growths that may appear on a dog, including lipomas, warts, cysts, skin tags, or cancerous lesions and tumors. 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 concerning. Needle aspiration is a very quick and simple process, or a punch biopsy is also straightforward and often only requires a local anesthetic (lidocaine block). Either diagnostic will enable you to have a 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 malignant 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 and tend to be harmless. Sometimes they will stop growing, but don’t often disappear or get smaller. Although these common old dog lumps are usually not dangerous, larger lipomas can cause discomfort or compromise mobility (e.g., infiltrative lipomas). Depending on where they are located, lipomas can cause also cause put pressure on internal organs. In very rare cases, more concerning tumors can be embedded within or beneath the lipoma. Therefore monitoring the lipomas and having then assessed by a veterinarian is important.

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 veterinarian will likely have their own take on this. For verified lipomas, the choice is either to leave them be (benign neglect), 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 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 and Adenomas

The term “warts” is often misused in veterinary medicine. Warts are caused by a viral infection (papillomaviruses). However, what most people call warts are sebaceous adenomas. This means they originate from the sebaceous glands. There are the oil-producing glands (sebum) associated with hair follicles and these glands are responsible for maintaining normal skin and hair health and a healthy skin barrier. These glands are more heavily concentrated on the paws, neck, chin, face, rump, and tail. See pictures below:

Sebaceous adenomas tend to grow outward on to the skin surface. These growths are narrower at the base and are often on a thin stalk. These growths will often ooze a yellow-white oily material. The growths are usually 4mm to 10mm in size and sometimes they might extend below the surface of the skin. Removal is usually curative, but removal is not usually necessary unless it is getting infected or irritated (sometimes self-mutilation). The prognosis is usually good. Sometimes, these can be more invasive. These are sebaceous adenocarcinomas.  These are more (locally) invasive, and removal is indicated.

Warts (also called papillomas) are another most common type of old dog lumps and can occur on your dog’s skin, on his eyelids, ear flaps, paw pads, between the toes, around the genital area, or in their mouths. See pictures below:

Warts 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. These are also seen secondarily to cyclosporine (Atopica^®) and oclacitinib (Apoquel^®) and sometimes there is a history of being at doggie day care.

Viral 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, as shown on the picture below:

Below is an example cyst near a dog’s eye:

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.

Treating sebaceous cysts in dogs: Sebaceous cysts are benign and generally do not need any urgent treatment. Some may resolve on their own (‘Come to a head’ and burst or ooze out the pus/gunk inside.) but may “fill-up” again as the cyst lining is still present. 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 (usually self-resolving transient cancerous) growth found on the skin of young dogs. Common areas affected include the ear flaps, face, feet, and legs. They are dome-shaped and red with no hair (button-like) These growths form when a type of immune cell (histiocyte) 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 at any age. Allergic dogs are predisposed. Most histiocytomas will heal without treatment in 2-3 months. However, in some cases, they can get worse with time. They can look concerning 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.

Below is a histiocytoma on a dog’s ear flap:

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 in appearance, but usually, they are fairly smooth, round growths visible on the skin surface. Other times they can look like a wart, adenoma or even a skin tag. When they develop beneath the skin surface, they can resemble other mases such as a benign fatty tumor (lipoma). The main objective is to differentiate between a histiocytoma and mast cell as they look very similar. Mast cell tumors need to be removed. Learn more in our article about “Mast Cell Tumors: a Veterinarian’s Guide for the Dog Owner“.

7. Melanoma and Melanocytomas

Melanoma tumors are dark and can be small, large, flat, or raised. They can appear as a solitary smooth surfaced pigmented nodule, a multilobulated nodule, or even somewhat flat. 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 and on the lip fold (black growth):

Melanomas/melanocytomas can be detected anywhere. Most malignant melanomas in dogs grow in/around the mouth or in other mucus membranes, but they can also be found in other areas. When present on mucous membranes, such as around the eyes or lip folds, the prognosis may be less favorable. These growths are also noted on toes (claw beds).

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. 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 rare, and they are not as aggressive in terms of spreading—usually focally. However, like some aggressive melanomas or high grade mast cell tumors are, these can spread (metastasis).

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 adenomas as well as 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. Hemangiosarcoma/Hemangioma 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. Luckily, what is usually found on the skin are benign blood vessel tumors known as melanocytomas. These are benign blood vessel growth. They may even be in part induced by extended periods of solar exposure. Read more: Hemangiosarcoma in Dogs: Our Vet Explains.

11. Anal Sac Tumors

Anal gland tumors are usually cancerous (The most aggressive ones are adenocarcinomas.) 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

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.

Pictures of Common Dog Lumps, Tumors, Warts, and Cysts

Click here to see more 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.