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Causes of a Lump on a Dog's Rib Cage

Lump on a Dog's Rib Cage

There can be several causes of a lump on a dog's rib cage and the only way to know for sure what you are dealing with is having the vet evaluate the lump. Dogs are prone to getting many types of lumps and bumps on their bodies and generally the majority of them will turn out being nothing serious, but occasionally dogs can get cancerous lumps on their rib cage too. A simple procedure can sometimes help determine the type of lump on a dog's rib cage and the best course of action. If there is a lump on your dog's rib cage, your best bet is to see the vet for proper diagnosis and treatment.

lump on a dog's rib cage

If your dog has a lump on the rib cage, see your vet.

A Lump on a Dog's Rib Cage

If your dog has developed a lump on the rib, your best option is to see your vet so to have it evaluated. Your vet will ask you several questions such as for how long you have noticed the lump and if there are any other symptoms.

By palpating the lump, the vet can already have a general idea on what a lump on a dog's rib cage may be, but the main, most accurate way to determine its nature is by taking a sample.

An easy test to determine the cause of a lump on a dog's rib cage is a procedure known as a "fine needle aspiration." In this test, the vet will use a small-gauge needle (fine needle) to aspirate a sample of cells or fluids to be analyzed. The vet may take samples from several areas of the mass.

The collected cells or fluids are then placed on a glass side and may be evaluated by the veterinarian under a microscope (in house) or the sample may be sent out to pathologist for evaluation. Results may be obtained immediately when the sample is analyzed in house, while when sent out to a lab, results may take anywhere between 3 and 5 days.

In some cases, the vet may need to surgically remove the lump and then biopsy it. What are some potential differentials for lumps on a dog's ribs? There are several possibilities. Below are several possible causes for lumps on a dog's rib cage.

Did you know? Sometimes people may feel a "lump" on the dog's last rib when in reality what they are feeling is the normal anatomy of a " dog's floating rib" along the dog's flank.


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Lipoma Lump on a Dog's Rib Cage

Lipomas are commonly found on dogs and they are simply benign masses made of fat cells. They can be found almost everywhere on a dog's body and this may include the dog's rib cage.

Generally, lipomas are quite easy to recognize being that they are mostly found just under the dog's skin and are not firmly attached to underlying structures. Lipomas are often round or oval and can feel soft and semi-squishy, meaning that tend to move freely under the skin when touched.

There are always though exceptions to the rules. For instance, at times, lipomas may also feel hard and feel as if attached when they're simply located between muscle layers, points out veterinarian Dr. Altman. Lipomas that are not encapsulated, and their fatty cells fatty cells are mixed throughout normal tissue, invading muscles, joint capsules and nerves, are known as infiltrative lipomas.

While lipomas have a classical feel, they should still be aspirated because there are growths that may appear innocent, when in reality they are cancerous. An example are mast cell tumors which are infamously known as "the great imitators."

Typically, when fine needle aspirates are done on lipomas, the aspirate will appear clear resembling oil drops on the slide, explains veterinarian Dr Gary. This is normal after all, considering that lipomas are made of cells of fat. Sometimes, based on how large or troublesome lipomas are, dogs may need dog lipoma surgery. 

"A fatty tumor stuck between the muscle layers of the abdominal wall can also feel very hard on palpation but do not cause serious problems." ~ Dr. Scott. 

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If the growth/lump developed suddenly and your dog has a history of having sustained an injury, then most likely the lump/growth is a result of that. In this case, there are different possible scenarios going on.

The lump may be a hematoma, which is simply a collection of blood under the skin when a blood vessel bursts as a result of injury. A hematoma can literally fill up with blood rapidly overnight.

In the case of a hematoma, the vet may need to open it up so that the blood vessel can be isolated and tied off to prevent any further bleeding.

Another possibility for a lump-like growth on the dog's ribs following an injury is the presence of an abscess which is basically a collection of pus. In the case of an abscess, it will have to be lanced and drained. The dog may also require a course of antibiotics.

In some cases, a hard lump may be indicative of bone changes from previous trauma to the rib. A callous formation may be found on the rib if the dog sustained an injury that could have caused a rib to crack or fracture.

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Soft Tissue/Skin Growths

In some cases, a lump on a dog's rib cage may be due to the presence of some cyst. Sebaceous cysts may feel very hard when palpating them and they require lancing and draining to correct the problem, further explains Dr. Scott. These may erupt from an oil gland that gets clogged and continues to grow.

Some forms of cancer may affect the dog's skin, nerves or tissues and include fibrosarcomas, neurofibromas, hemangiopericytomas and, soft tissue sarcomas. There are, of course, several more types of benign or malignant skin growths that may be possible. Several of these growths may require surgical removal.

Picture of cancer cells

Picture of cancer cells

Rib Bone Cancer in Dogs 

If the dog has a growth that is hard like bone and that's attached to the rib, there are always chances for cancerous growths. These cancerous growths may be benign or malignant. There are two main types of cancer of the dog's ribs: osteosarcomas (cancer of the bone) and chondrosarcomas (cancers of the cartilage).

Osteosarcoma of the rib is a very aggressive cancer with a high metastatic rate (spreading to other body parts). When localized to the rib, this form of cancer tumor spreads much faster than bone cancer affecting the leg even when it's surgically removed, explains veterinary oncologist Dr. Heather M. Wilson. Bone cancer of the dog's rib may result in respiratory compromise.

Generally, the median survival time of bone cancer of the rib is only 3 months. According to a study, bone cancer of the ribs affected in most cases ribs 5 through 9 with the right side being twice as much affected compared to the left side. Only less than 10 percent of the affected dogs survived more than 4 months after diagnosis.

While not as malignant as osteosarcoma, chondrosarcomas can affect life span as well, causing affected dogs to live anywhere between a few months to a few years. Chondrosarcomas are often found on flat bones such as the ribs and bones of the skull. While this type of rib tumor isn't usually painful, since it has a tendency to grow inward, it can lead to lung compression, explains veterinarian Dr. Anne. 

If the vet suspects cancer or determines there is cancer, it's important to have chest x-rays carried out. If there are signs the cancer has spread to the lungs, sadly prognosis changes dramatically.

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  • J Am Vet Med Assoc. 1982 Apr 15;180(8):927-33. Malignant neoplasia of canine ribs: clinical, radiographic, and pathologic findings. Feeney DA, Johnston GR, Grindem CB, Toombs JP, Caywood DD, Hanlon GF.
  • J Am Anim Hosp Assoc. 1995 Jan-Feb;31(1):65-9.Primary rib tumors in 54 dogs.

    Pirkey-Ehrhart N, Withrow SJ, Straw RC, Ehrhart EJ, Page RL, Hottinger HL, Hahn KA, Morrison WB, Albrecht MR, Hedlund CS, et al.

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