Lumps & Bumps On a Dog’s Chest or Rib Cage [Vet Advice]

This article was updated on April 26th, 2023

Lumps and bumps on dogs’ chests and rib cages are a common finding in our vet clinic, especially in older patients. We frequently see benign masses like lipomas, sebaceous cysts, and adenomas, as well as other types of lumps and bumps like abscesses and occasionally malignant growths. In this article, we’ll take a look at some of the common and less common lumps we see on dogs’ rib cages.

Are lumps and bumps on a dog’s chest or rib cage serious?

While many benign types of lump can be seen on the rib cage, there are, unfortunately, also many malignant tumors that can develop in this area. Many of these are treatable, especially if caught at an early stage, so it’s important to have any new lumps checked by your vet to ensure malignant lumps are identified and treated as early as possible.

What are the notable differences between the types of lumps and bumps?

Lumps on the rib cage can be incredibly varied, but there are some common factors that can help to determine the likely diagnosis. One of the main things that determines the possible cause of a lump is where the lump is relative to the skin. This article is therefore divided into lumps under the skin, those on the skin, and lumps associated with the ribs, as well as being divided into benign and malignant causes.

Many of these lumps have various similarities and differences – read on for more information about these different lumps, how to spot them, and what treatment they’re likely to need.

Benign lumps under the skin on the chest or the rib cage

1. Lipomas (fatty lumps)

Lipomas are one of the most common lumps I see on dogs’ chests in our practice. These benign (non-cancerous), slow-growing tumors develop from fat cells under the skin. They can be any size and are usually smooth, soft, and non-painful. The overlying skin usually appears normal and moves easily over the lump.

Lipomas are benign, so do not require treatment unless they grow very large or get in your dog’s way. Occasionally, other lumps like mast cell tumors can appear similar to a lipoma, so it’s worth discussing a fine needle aspirate biopsy with your vet to rule out other types of lump that may require treatment. Learn more about lipomas in dogs.

2. Abscesses

Abscesses and swelling due to infection are less common on the rib cage as they usually occur as a result of a wound. Occasionally, small wounds may go unnoticed in this area and allow infection. Rarely, foreign objects like grass seeds can migrate under the skin and cause an abscess to develop in this area.

Abscesses usually develop rapidly and are painful to your dog. They often appear red and inflamed and may ooze pus or discharge. If any lump appears angry and painful, you should get this checked by your vet as soon as possible, as infections often worsen and spread over time. In the meantime, preventing your dog from licking or scratching the area is essential, and if discharge is present, gentle bathing with dilute salt water may help.

The prognosis for these lumps is usually good, although it depends on the severity and what has caused the abscess or infection to develop. Treatment usually involves cleaning the area, antibiotics, and pain relief. Some cases may require the abscess to be drained or surgically explored under sedation or anesthetic.

3. Injection site reactions

If your dog develops a lump shortly after receiving an injection (e.g. a vaccination) this is usually a benign, mild inflammatory reaction to the injection. These typically occur in the scruff area over your dog’s shoulder blades. The area may feel a little ‘thickened’, or a more defined lump may be present, and this can be a little itchy. This usually resolves over a few days to a week.

In rare cases, a more severe inflammatory reaction can cause a large, firm, irregular mass to develop in the area after an injection. This may take several weeks to resolve.

If you notice a small, non-painful lump appear shortly after an injection and your dog is otherwise well, monitoring it over the next few days is a reasonable option. If the lump is large, painful, or persistent, or you have any other concerns, it’s best to check with your vet. The scruff area can be more prone than others to soft tissue sarcomas, a type of malignant tumor, so it’s important not to ignore any persistent lumps.

4. Ribs!

It might seem obvious that ribs are found in the rib cage – but in some dogs these ribs can be mistaken for lumps. I’ve seen a number of owners concerned about their puppy or young dog due to a previously unnoticed ‘lump’ on the chest.

In all dogs, the last pair of ribs is described as ‘floating.’ These ribs are short and end partway down the chest, not connecting to the sternum at the bottom of the chest. In some dogs, these last ribs may protrude a little and cause a visible ‘bump’ under the skin. Similarly, in some dogs, the rib cage itself may be ‘flared out’ and appear to stick out. In some cases, this is due to the shape of the breed, while others are due to individual variation.

Benign lumps on the skin of the chest or rib cage

1. Sebaceous cysts

Sebaceous cysts are common and develop when a pore or follicle becomes blocked, causing oily secretions to accumulate. They are usually slow-growing, firm, or fluid-filled on palpation and range from a few millimeters to a few centimeters in diameter. Many dogs will only develop one cyst whilst in some, several develop over time. Occasionally, if the contents of the cyst leak out into the surrounding tissues or infection occurs, there may be inflammation and pain, but these are usually non-painful.

These are often diagnosed based on the appearance of the material within the cyst when a fine needle aspirate is taken. It is important not to assume a new lump is a cyst (even if your dog already has other cysts), as other types of lump may be mistaken for a cyst. Most cysts do not require treatment, but if they become infected or inflamed, medication and/or surgical removal may be recommended. Learn more about sebaceous cysts in dogs.

2. Benign sebaceous gland tumors

These lumps, including sebaceous adenomas and epitheliomas, are benign tumors associated with sebaceous (secretory) glands. This kind of benign growth is relatively common in middle-aged to older dogs. Some dogs develop multiple lumps associated with the sebaceous glands due to a benign condition known as sebaceous hyperplasia.

You can also check this picture on DermVets.com for another example. These tumors often appear similar to warts: raised, hairless, often pale pink but sometimes pigmented small lumps, usually growing slowly and remaining under 2.5 cm in diameter. They can be smooth or have an irregular surface like a wart and occur anywhere on the skin, including the chest.

These benign lumps usually do not require treatment unless they are causing irritation, in which case surgery is usually curative. These are often diagnosed based on clinical examination, but to definitively rule out a malignant tumor (e.g. a sebaceous adenocarcinoma), a fine needle aspirate or biopsy may be recommended.

3. Warts and skin tags

Papillomas, also known as warts, are relatively common in young dogs. They are caused by a papilloma virus and typically resolve in several weeks to months. They appear as raised, irregular, ‘cauliflower-like’ small lumps anywhere on the body (including the chest), although they are typically seen on the face and neck.

Skin tags are benign growths of the skin that may appear anywhere, at any age, although they are more common in older dogs. They are usually small, soft, and fleshy and do not cause irritation unless they are caught on objects. In the chest area, nipples may occasionally be mistaken for skin tags.

Neither of these lumps typically requires treatment unless they are causing irritation or a wart is failing to resolve; however, if you notice a new or changing lump, it’s still recommended to get this checked by your vet to rule out any more serious diagnoses. View more pictures of dog warts or skin tags.

4. Urticaria (hives)

Hives are a not uncommon inflammatory response to a range of possible factors, including insect bites, food allergies, medications, and environmental irritants, including pollen or chemicals. They can occur in any dog and often appear very rapidly, causing raised, itchy, variably sized red bumps or welts across the face and body, including the chest.

Or click here to view another picture from EthosVet.com.

In severe cases, swelling of the face, lips, and throat may occur, which can be life-threatening. If you notice swelling in these areas or difficulty breathing, you should seek urgent veterinary attention.

Hives will often resolve over a few hours to a few days, but veterinary treatment can often accelerate this and help prevent complications, especially in more severe cases. This typically includes antihistamines and/or corticosteroids. Depending on the severity of the reaction and whether any cause has been identified, your vet may also recommend further investigations, such as a food trial or blood testing, to try to identify an underlying cause.

If the cause of the hives is identified, avoiding the trigger or allergen is the best option. Home remedies such as oatmeal baths or cold compresses may provide some relief for mild cases of hives, but it is always best to consult with a veterinarian for proper diagnosis and treatment. Learn how to treat dog hives at home.

5. Histiocytomas

Histiocytomas are a relatively common benign skin tumor typically seen in young dogs. They are usually small (< 2cm), round, raised, pink to red hairless lumps, which do not cause significant pain or irritation despite often appearing inflamed. They are more common on the head, neck, and ears but can occur on the chest area.

These lumps are benign and regress without treatment in weeks to months; however, they can grow rapidly and appear similar to malignant masses (e.g. mast cell tumors), so testing is often recommended to rule this out.

1. What it looks like and how dog owners can recognize this is the issue (e.g. single bald patch vs. broader hair loss, red, irritated skin or not, etc.)
2. An assessment on how serious and/or frequent this issue is in dogs (Prognosis and/or prevalence) – is the hair loss going to get worse?
3. What owners can do at home (if relevant): possible home remedies, is it ok to wait and see, does it ever go away on its own?
4. Veterinary treatment: At what point is the vet needed (if relevant), with a description of veterinary treatments

Malignant soft tissue tumors of the chest

1. Mast cell tumors

Mast cell tumors are a common malignant skin tumor that can occur in any dog, although it is more likely in older dogs and certain breeds (e.g. Boxers). These tumors can develop anywhere in the skin and have a very variable appearance. They often appear as rapidly growing, raised, superficial masses that are often red, inflamed, and itchy, potentially with ulceration of the skin surface. However, some may resemble a benign lipoma lying beneath the skin and causing no visible irritation. One sign of a mast cell tumor is a lump that fluctuates in size, as these masses can release inflammatory mediators, which cause temporary swelling.

Mast cell tumors can be very serious, and the prognosis for an aggressive ‘high-grade’ mast cell tumor is relatively poor. However, many mast cell tumors are ‘low grade’, and surgical removal is usually curative in these cases. Mast cell tumors are usually easily diagnosed by fine needle aspirate, but in order to grade the tumor, a biopsy is usually required. Treatment usually involves surgical removal, and your vet will often recommend submitting the mass for histology in order to grade it (see how aggressive it is) and determine whether the mass has been fully removed. Your vet may also recommend ‘staging’ to check whether the tumor has spread elsewhere, including local lymph nodes, the spleen, and the liver.

If you notice any new rapidly growing mass, it’s important to get this checked sooner rather than later. The longer a mast cell tumor is left, the more likely it is to have spread (metastasized), which worsens the prognosis. Even if a mass is growing slowly and not causing irritation, these tumors aren’t always obvious – if you have any concerns about a lump, it’s worth discussing a fine needle aspirate with your vet to rule out a mast cell tumor. View pictures of Mast Cell Tumors.

2. Soft tissue sarcomas

Soft tissue sarcomas account for around 15% of all skin tumors in dogs. They are a group of malignant tumors, including fibrosarcoma, which usually occur as solitary, slowly growing masses in older dogs. Sarcomas may occur superficially in the skin or deeper beneath it and are typically firm, non-painful, and irregular in shape. These tumors can be seen anywhere on the body, with the chest and trunk being relatively common locations.

Treatment for these tumors consists of surgical removal, and this can be curative. These tumors often grow into the surrounding tissues, however, so local recurrence is relatively common. Due to this, wide surgical margins are often required to fully remove the tumor, which can be difficult is the tumor is large; catching these tumors in the early stages is important.

Diagnosis will usually involve either a biopsy or surgery, followed by sending the mass away for further analysis. Occasionally, these tumors can be diagnosed by fine needle aspirate, but they often do not provide a good sample using this method.

3. Melanomas

Melanomas can occur anywhere on the skin of any dog, although they are usually seen in older patients. They constitute 7% of malignant tumors in dogs; however, while melanomas on the toes and mouth are frequently highly malignant, those on the skin of the rest of the body are more typically benign.

This picture from WalkerVilleVet.com.au is another good example. On the chest or rib cage, melanomas are usually solitary, raised, round, or irregularly shaped darkly pigmented (black or brown) masses. Occasionally, however, melanomas do not have any pigment. If benign, these masses usually grow slowly.

These tumors may be diagnosed based on a fine needle aspirate, but a more in-depth analysis of a larger biopsy sample (or the whole mass after surgical removal) is usually required to determine whether the mass is benign or malignant definitively.

Treatment for melanomas usually involves surgical removal. If the mass is found to be malignant, further ‘staging’ is usually recommended to rule out metastatic spread to other organs, and if this is identified, further treatments like chemotherapy may be required. The prognosis depends on the location of the tumor, how aggressive it is, and whether or not it has spread. Early diagnosis of malignant melanomas is critical for the best possible outcome.

4. Mammary masses

Mammary tumors are very common in intact older female dogs. Spaying at a young age is reportedly protective against developing this tumor later in life, especially if your dog is spayed before her first season. The chain of paired mammary glands in dogs extends from between the back legs up to beneath the chest, and tumors can develop in any of these glands, meaning any lump under your dog’s chest could be related to the mammary glands.

These tumors develop beneath the skin and are associated with the mammary glands, often adhering to the overlying skin. They are usually relatively firm, often irregular in shape, and can be any size. As they progress, some may cause irritation or changes to the overlying skin.

While fine needle aspiration can assist in diagnosing mammary tumors, a larger biopsy is typically required to determine if the tumor is benign or malignant. Additionally, if the mass is malignant, it is important to check for the presence of cancer in other areas, such as other mammary glands, lymph nodes, and lungs.

Typically, surgical removal is the main treatment option, although chemotherapy may also be considered in certain cases. The extent of surgery required depends on the type, size, and spread of the tumor. The success rate of the surgery is highest with smaller tumors, with those less than 1 cm having a good prognosis, while those larger than 3 cm are less likely to have a positive outcome.

Malignant tumors associated with ribs

These tumors are relatively rare in dogs. Tumors affecting the bones are more common in the legs than over the chest area. With these tumors, you would be likely to notice a specific area of immovable hard swelling associated with a rib, which may also be painful. Any lump of this type is likely to require sampling for a definitive diagnosis, but your vet may be reasonably convinced of a presumptive diagnosis based on their clinical examination.

1. Osteosarcoma

Osteosarcoma is the most common type of rib tumor, although tumors of the ribs are relatively uncommon in dogs. These tumors are malignant and metastasize (spread) quickly. They can occur in any dog, although middle-aged to older dogs are more commonly affected.

Treatment options include surgical removal and/or radiation therapy with possible chemotherapy. With treatment, the average survival time of the patient is six months to just under two years.

2. Chondrosarcoma

The second most common tumor of the ribs is chondrosarcoma. This tumor arises from the cartilage of the rib. It is malignant but does not metastasize as often or as quickly as osteosarcoma. 

Chondrosarcoma typically occurs in middle-aged to older dogs and can occur in any dog, although some breeds may be more commonly affected.

Chondrosarcoma can be considered cured with complete surgical removal if “clean” (cancer-free) margins are obtained.  In areas where complete removal of the cancerous tissue was not possible, the tumor will probably recur, although slowly.  Your veterinarian may want to do a second surgery, or depending on your dog’s age, it may be appropriate to monitor the area instead of repeating the surgery.

Frequently asked questions

Are there any symptoms I should look out for if my dog has a new lump?

If the lump is inflamed or painful, oozing any discharge, or your dog seems bothered by it (e.g. licking and chewing) these lumps should be assessed as soon as possible.

Other things to look out for include your dog becoming more lethargic, gastrointestinal signs like vomiting and diarrhea, and drinking more water than usual. It’s also very important to monitor your dog’s weight, as some tumors can cause significant weight loss.

Any of these may indicate a systemic problem like a severe infection, inflammatory reaction, or in some cases, a malignant tumor that has spread to other organs.

Are there any signs I should go back to my vet about a mass we’ve decided to monitor?

If a mass is suspected to be benign or has been sampled and shown to be benign, you may decide with your vet to monitor it. It’s helpful to take regular photos or measurements so you can keep track of any changes. If you notice any of the following, we recommend returning to your vet:

• Sudden rapid growth
• Change in appearance, irregular growth (nodular, uneven as opposed to smooth and round)
• Ulceration 
• Oozing or weeping fluid or pus
• Bleeding
• Painful to the touch

When should I see a vet about a new lump?

We recommend seeing your vet about any new lump you notice, as it can be difficult to determine whether they are benign or malignant and whether any treatment is required at home.

If a lump is small, growing very slowly, and causing no irritation, it may be reasonable to wait a short time for a convenient appointment for the lump to be assessed. If you notice a rapidly developing lump, any pain, irritation, or discharge, or any other symptoms like those mentioned above, we would recommend seeing your vet as soon as they have an available appointment.

How are lumps and bumps diagnosed?

Not every mass requires a biopsy for diagnosis. There are some lumps that your veterinarian will feel comfortable presumptively diagnosing without a sample. They might treat this lump medically or take a conservative approach and monitor it over time for any changes. The only way to be one hundred percent certain that a lump is benign (not cancerous), however, is for a veterinarian to take a small sample of the lump and have it looked at under a microscope. For some lumps, a fine needle aspirate is sufficient. This is usually done consciously and involves a small needle (like those used for vaccination) being used to take a tiny sample of cells or other material (e.g. pus from an abscess). For some masses, a definitive diagnosis requires a larger biopsy, which is often taken under sedation or anesthetic. If the lump is small, but your vet is concerned it may be malignant; they may recommend fully removing it and submitting it for further analysis under a microscope for a definitive diagnosis.

The costs of diagnosing a lump depend on the testing required. The cost of an exam for your dog ranges from $50 to $200 nationally, while the average price for a fine needle aspirate is $20-$100. A biopsy is anywhere from $400-$800.  The price is greater than the FNA due to the need for sedation and the method for preparing the tissue sample.  

Will a vet be able to help over a video call?

In most cases, it is much easier for a vet to accurately assess a dog’s lump in person as they are able to feel the mass and check over the rest of your dog to identify any other concerns like weight loss or enlarged lymph nodes (due to infection or spread of a malignant tumor).

If you are not able to see your vet quickly, a video call may be a good way to get a vet’s opinion on how urgently your dog needs to be seen and what the most likely diagnoses are. It is unlikely they will be able to provide a specific diagnosis, but knowing the most likely diagnosis (e.g. that a lump is most likely a lipoma) may give you some peace of mind whilst waiting to see your vet.

What treatments are available for these lumps?

Unfortunately, we can’t cover all the possible treatments for these lumps in this article – there are many possible treatments depending on many factors, including the type of lump, its size and location, your dog’s overall health, and cost considerations.

For abscesses and swellings due to infection, a combination of pain relief and antibiotics is often required. In some cases, however, surgical exploration or lancing of the lump may be required to help it drain and heal.

For tumors, surgical removal is still the main treatment option. However, the extent of surgery depends on how malignant the mass is, the type of mass, and its location, as some areas e.g. the armpit area, are more difficult to operate on due to the amount of movement post-operatively causing wound breakdown. There are an increasing number of other treatment options including various types of chemotherapy and radiotherapy; however, these are usually used alongside surgery if needed to treat residual cancer cells or those that have spread to elsewhere in the body.

Does it tell you anything about the lump if it is hard or soft?

Generally, harder lumps are more concerning than soft lumps beneath the skin. This is mainly due to the fact that benign lipomas (one of the most common types of lump found under the skin) are soft; the fact that a lump under the skin is hard rules out the most common benign diagnosis. There are still other types of benign lumps that are firmer, so this isn’t a reason to panic, but it is a good reason to get a lump checked.

Soft lumps are more likely to be benign lipoma, but this is still not definite – some lumps, like mast cell tumors, can be very soft on palpation. This is why we recommend keeping a close eye on any lump and discussing with your vet further testing for any new lump.

Similarly, some lumps are more firmly attached to underlying tissues while others move around easily, either under the skin (like a lipoma) or with the skin if they have grown from it. Any lump that feels firmly fixed in position is more concerning, as malignant lumps are more likely than others to grow into surrounding tissues.

Do lumps hurt dogs when touched?

Most lumps do not hurt when touched. As mentioned above, a lump that is irritated or seems painful may be infected or may suggest the lump is malignant. Either of these is a good reason to get the lump checked by your vet – benign lumps should not hurt your dog.

References

Fonseca-Alves, C.E. et al. (2021) “Current status of canine melanoma diagnosis and therapy: Report from a colloquium on canine melanoma organized by Abrovet (Brazilian Association of Veterinary Oncology),” Frontiers in Veterinary Science, 8. Available at: https://doi.org/10.3389/fvets.2021.707025. 

Jackson, H. and Marsella, R. (eds) (2012) BSAVA Manual of Canine and Feline Dermatology. 3rd edn. British Small Animal Veterinary Association. 

Stefanello, D. et al. (2008) “Marginal excision of low-grade spindle cell sarcoma of canine extremities: 35 dogs (19962006),” Veterinary Surgery, 37(5), pp. 461–465. Available at: https://doi.org/10.1111/j.1532-950x.2008.00408.x.