4 Types of Carcinoma in Dogs

Written by Jennifer Geer
Published: March 26, 2023
© Roger costa morera/Shutterstock.com
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It’s not something pet owners want to think about, but dogs get cancer at about the same rate as humans. It’s helpful to know there are treatments available for your pet. And even better, more cancer treatments every day are being developed specifically for dogs. If you’re a dog owner, you may be wondering how to recognize early warning signs and what treatments are available.

Carcinoma is a type of cancer that begins in the skin and tissues that line the internal organs. Humans and animals can develop carcinoma. It has several different subtypes. 

Read on for a look at four types of carcinoma that can develop in dogs, including treatments and early symptoms to watch out for.

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1. Intestinal Cancer (Adenocarcinoma)

dog ultrasound
If adenocarcinoma of the intestines is suspected, ultrasound can be used to help diagnose your dog.


Adenocarcinoma is a type of carcinoma that develops in the glands that line your organs. It’s a malignant tumor that invades the tissue. 

In humans, it can cause cancer of the:

  • Breast
  • Stomach
  • Lung
  • Pancreatic
  • Colon

In dogs, adenocarcinoma may develop in the gastrointestinal system, including the intestine, stomach, and rectum. This type of cancer is rare in dogs. However, when it does occur, intestinal cancer tends to affect middle-aged to older dogs, at least over six years of age. It’s more common in male dogs than in females. The reason why some dogs develop intestinal cancer is still unknown.

What are the early symptoms of intestinal cancer in dogs to watch out for?

You may notice symptoms in your dog that affect your pet’s gastrointestinal system. 

Early symptoms can include:

  • Poor appetite
  • Weight loss
  • Vomiting
  • Diarrhea
  • Red blood in feces, or black feces

How do vets diagnose intestinal cancer?

Be prepared to talk to your veterinarian about the history of your dog’s health and symptoms. Your vet will likely run tests such as blood work and fecal samples. If adenocarcinoma of the intestines is suspected, ultrasound can be used to help diagnose the animal. Your vet may collect sample biopsies as well.

What are the treatments for intestinal cancer in dogs?

Sadly, this type of cancer spreads easily in dogs, making it more difficult to cure. Though surgery is used to remove the tumors, it can be hard to remove the affected tissue completely. This is especially true in the stomach and intestines. 

If the cancer has spread, your vet may prescribe chemotherapy for your dog. Your dog will likely need painkillers to feel more comfortable during treatments. Unfortunately, with intestinal cancer, the prognosis is not always a good one.

2. Basal Cell Carcinoma

dog at vet
Basal cell carcinoma is a slow-growing type of skin cancer, which if caught early, has a good prognosis.


Basal cell carcinoma is a malignant type of skin cancer that starts in the basal cells. It’s a common form of skin cancer for both humans and dogs. Luckily, this type of cancer is slow-growing, and if caught early, the prognosis can be good. Furthermore, if the tumor is completely removed, most dogs can go on to make a full recovery.

A basal cell tumor is an abnormal growth that develops from an uncontrolled division of basal cells. Basal cells are the cells that make up the bottom layer of the outermost layer of skin. Basal cell tumors are common in both dogs and cats. When the basal cell tumor is malignant, it’s called basal cell carcinoma.

What are the early symptoms of basal cell carcinoma in dogs to watch out for?

The tumor will be a raised lump that can range in size from a few centimeters to inches. It’s usually a hairless mass appearing in the skin, most often found on the head, neck, or shoulders. The lumps may be pigmented.

How do vets diagnose basal cell carcinoma?

Your vet will perform a biopsy of the mass, either surgically, or using needle aspiration. The sample will need to be examined by a veterinarian pathologist who can see if the tumor is benign or malignant. 

What are the treatments for basal cell carcinoma in dogs?

Removing the mass is the standard treatment. It can be done on smaller tumors through cryosurgery, which is using liquid nitrogen to freeze the tumor. The surgeon will try to remove the entire tumor to prevent the mass from regrowing.

3. Squamous Cell Carcinoma (Tumor of Skin Cells)

Dog having surgery
Surgery to remove the lesion is usually the best treatment for squamous cell carcinoma with a good prognosis if the tumor is completely removed.


Squamous cell carcinoma is a common type of skin cancer in both humans and dogs. It develops in the squamous cells, which are the cells that make up the middle and outer layers of the skin. It can be aggressive, but it’s slow growing, and usually, successfully cured with proper treatment.

Exposure to ultraviolet (UV) radiation from sunlight or tanning beds is what causes this type of cancer in humans. Squamous cell carcinoma is more common in dogs that spend more time outdoors or live at higher altitudes. The risk tends to increase with age.

What are the early symptoms of squamous cell carcinoma in dogs to watch out for?

The symptoms may be hard to spot. Squamous cell carcinomas can be found anywhere on a dog’s body. They may look like a sore, bump, or lesion. It’s often seen on the nose, toes, and legs. It may look like a bleeding sore that doesn’t heal even with antibiotics.

How do vets diagnose squamous cell carcinoma?

As with basal cell carcinoma, this type of cancer can be diagnosed using fine needle aspiration or a surgical biopsy. Your vet will want a complete health history from you on your dog, and will likely run blood counts and blood chemistry tests as well. 

What are the treatments for squamous cell carcinoma in dogs?

Fortunately, this type of cancer is unlikely to spread to nearby lymph nodes and other organs. Surgery to remove the lesion is usually the best treatment. Typically vets will not recommend radiation or chemotherapy. The prognosis is usually good if surgery can remove the tumor completely.

4. Mammary Carcinoma

Dog post-surgery
If your dog is diagnosed with mammary carcinoma, surgery will be needed to remove the tumors.


Mammary tumors in dogs can be benign (non-cancerous) or cancerous. A mammary carcinoma or adenocarcinoma is cancerous (malignant). This cancer is more common in unspayed females or females that weren’t spayed until after their first heat cycle.

Moreover, mammary carcinoma also tends to occur more often in certain breeds such as toy poodles, miniature poodles, German shepherds, and cocker spaniels.

What are the early symptoms of mammary carcinoma in dogs to watch out for?

Unless your dog has a noticeable mass or lump under her skin, it can be hard to detect mammary carcinoma. Sometimes your vet can feel a lump in a routine exam. Or you may notice a mass or lump underneath your dog’s skin along her abdomen. It may occur next to a nipple. The mass might bleed or be painful to the touch. You may also notice a change in your dog’s behavior. For example, she may be more fatigued, have a loss of appetite, or experience weight loss.

You may also see swelling, redness, and pain in a dog’s mammary glands. This can indicate inflammatory mammary carcinoma, which is a subtype of mammary carcinoma.

How do vets diagnose mammary carcinoma?

After a physical exam to feel the lump, your vet may also want to perform a fine needle aspiration or biopsy to test the tissue. If the tumor is found to be malignant, your vet may additionally check your dog to see if the cancer has spread to other parts of her body. Your vet may also order blood tests, urinalysis, X-rays, or ultrasounds. 

What are the treatments for mammary carcinoma in dogs?

The treatment depends on the size of the mass and whether or not cancer has spread to other parts of your dog’s body. Surgery will be needed to remove the lump. Your vet may recommend chemotherapy or radiation as well if cancer has spread.

The prognosis depends on whether or not the cancer has spread to other parts of the dog’s body. Early detection is key to catching the cancer before it spreads.

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About the Author

Jennifer is a professional writer living in the Chicago area. She owns two pugs. Or rather, they own her. Jennifer has discovered that her best writing happens against a backdrop of soft pug snores.

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