As dog owners, we view our pets as cherished family members. Our greatest wish is to see them stay healthy and by our sides for as long as possible. However, one of the most concerning health issues for any pet owner is "Cancer." Whether it is canine skin cancer, lymphoma, or liver cancer, these conditions are not only challenging to treat but also directly impact our dogs' quality of life and overall happiness.

The key to effectively managing this disease lies in recognizing the early warning signs. Detecting cancer in its initial stages often leads to better disease control and a longer, higher-quality life for our pets. This guide covers 7 common cancers in dogs to help you monitor your furry companion's health and identify abnormalities before they become critical.

7 Common Cancers in Dogs and Initial Care Guidelines

1.Mast Cell Tumor & Others

Skin cancer is one of the most frequently diagnosed cancers in dogs, particularly in those with thin, light-colored coats or those with prolonged exposure to intense sunlight. Causes can range from genetics and chronic inflammation to UV radiation. The most prevalent type is the Mast Cell Tumor (MCT). Mast cells are part of the immune system found in the skin; when they grow abnormally, they can develop into cancerous masses that expand rapidly. 

Symptoms to Watch For 

• A raised lump or mass on the skin that grows quickly.
• The lump may appear red, swollen, or develop into an open sore (ulcer).
• In some cases, multiple lumps may appear in different locations across the body.

Treatment Guidelines for Canine Skin Cancer 

Currently, a Biopsy or Fine Needle Aspirate (FNA) is the only definitive way to confirm if a mass is a Mast Cell Tumor. The primary treatment for skin cancer in dogs is usually surgical excision. In more advanced or aggressive cases, surgery may be supplemented with radiation therapy or chemotherapy.

2.Mammary Tumor

In addition to skin cancer, mammary tumors are among the most common cancers diagnosed in female dogs, especially those that have not been spayed before the age of two. This is because female hormones significantly stimulate the growth of mammary tissues. 

Symptoms to Watch For 

• One or more lumps felt around the mammary glands (teat area).
• Swelling, redness, or open sores (ulceration) on the skin over the glands.
• In some cases, abnormal discharge or blood leaking from the teats.

Treatment Guidelines for Mammary Tumors in Dogs

Initially, the veterinarian will evaluate the condition through X-rays, ultrasounds, and a biopsy. If detected in the early stages, surgical removal of the tumor is usually the primary treatment. Additionally, spaying the dog alongside or after surgery can help reduce the risk of recurrence. 

3.Lymphoma

Lymphoma is a cancer caused by the abnormal growth of lymphocytes, a type of white blood cell essential to the immune system. This cancer can affect many breeds but is most frequently observed in Golden Retrievers and Labrador Retrievers. 

Symptoms to Watch For 

• Swollen lymph nodes, particularly around the neck, armpits, or groin area (often felt as firm, painless lumps).
• Weight loss, loss of appetite, and general lethargy.
• In some cases, fever or difficulty breathing may occur.

Treatment Guidelines for Lymphoma in Dogs  

Lymphoma is often highly responsive to chemotherapy. To determine the best course of action, the veterinarian will perform blood tests and a biopsy to stage the disease and develop a personalized treatment plan at the hospital. 

4.Osteosarcoma

This type of cancer is frequently found in large breed dogs, such as Rottweilers, Great Danes, and Golden Retrievers. It typically develops in the bones of the front and hind legs, particularly around the knee or shoulder joints. 

Symptoms to Watch For  

• Unexplained limping or lameness.
• Visible swelling or a firm lump on the legs or near the bones.
• In some cases, "pathologic fractures" may occur, where the bone breaks easily due to being weakened by the tumor. 

Treatment Guidelines for Bone Cancer in Dogs 

An X-ray and biopsy are required to confirm the diagnosis of osteosarcoma. If confirmed, the primary treatment usually involves surgery combined with chemotherapy to control the spread (metastasis) of cancer cells to other organs, such as the lungs. 

5.Liver Cancer

Liver cancer can either originate directly within the liver (primary) or occur when cancer from other organs spreads (metastasizes) to the liver. It is most commonly diagnosed in senior dogs or those with pre-existing chronic liver disease. 

Symptoms to Watch For 

• Loss of appetite, vomiting, or chronic diarrhea.
• Abdominal swelling (distension) or fluid accumulation in the abdominal cavity (ascites).
• Unexplained weight loss.

Treatment Guidelines for Liver Cancer in Dogs

Diagnosis typically involves an ultrasound and blood tests to evaluate liver function and identify abnormalities. If the cancer is detected in its early stages before it has spread, surgical removal of the tumor can significantly improve the treatment outcome.

6.Oral Cancer

Oral cancer is primarily found in senior dogs, particularly in breeds with wide mouths such as Golden Retrievers or Schnauzers. These tumors commonly develop on the gums, tongue, or lips. 

Symptoms to Watch For  

• Visible lumps or non-healing sores in the mouth.
• Abnormally strong or foul breath (halitosis).
• Difficulty eating (dropping food) and excessive drooling. 

Treatment Guidelines for Oral Cancer in Dogs  

The veterinarian will utilize X-rays or a CT Scan to assess the extent of the tumor's invasion into the jawbone or surrounding tissues. Treatment plans typically involve a combination of surgery, radiation therapy, and chemotherapy, depending on the specific type and stage of the cancer.

7.Lung Cancer

Lung cancer in dogs is less common compared to canine skin cancer and the other types mentioned above. However, once it occurs, rapid diagnosis is critical, as early detection significantly impacts treatment options and long-term outcomes.

Symptoms to Watch For 

• Chronic coughing, panting, or labored breathing.
• Easily fatigued (exercise intolerance) and unexplained weight loss.
• In some cases, fever or coughing up blood may occur.

Treatment Guidelines for Lung Cancer in Dogs 

Initially, the veterinarian will diagnose the condition using chest X-rays and a CT Scan. Treatment plans depend on the tumor's location and stage, which may involve surgical removal of the affected lung lobe or chemotherapy.

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Early Detection for a Longer, Healthier Life 

Cancer in dogs is a serious condition that should never be overlooked, as it can affect pets of any age or breed. Understanding common cancers, such as Mast Cell Tumors and the others mentioned, empowers owners to remain vigilant and identify abnormal signs early. The sooner cancer is detected, the more effective the treatment and the better the chances of recovery.

For comprehensive pet healthcare under international standards, visit Thonglor Pet Hospital. Our 24-hour facility is staffed by experienced veterinarians and equipped with the latest diagnostic technology and a fully prepared emergency room. We are dedicated to ensuring every dog enjoys the best health and quality of life possible. For inquiries, please call 02-079-9999 or contact us via Line Official @jaothonglor.

References:

1. 12 Types of Cancers in Dogs and Cats. Retrieved on October 10, 2025, from https://ccr.cancer.gov/comparative-oncology-program/disease-info 
2. Mast Cell Tumor (Mastocytoma) in Dogs. Retrieved on July 24, 2025, from
   https://wvj.science-line.com/attachments/article/85/WVJ15(1)31-41,%202025.pdf