What Are Nasal Tumors in Dogs? (AKC)

A tumor is an abnormal mass of cells that arises when cells reproduce too quickly or don’t die off when they should.

• Tumors can be malignant (cancerous), which means they can grow quickly, invade other tissues, and spread throughout the body or they can be benign, which means they usually grow slowly and don’t spread or invade other tissues.
• Rachel St-Vincentis a specialist in radiation oncology at Schwarzman Animal Medical Center in New York City. She elaborates, “Nasal tumors are tumors that arise from inside of the nasal cavity, including the sinus as well as the nasopharynx. They can be benign or malignant. However, malignant tumors are more common.”
• Benign nasal tumors in dogs typically come in the form of polyps, which are caused by chronic inflammation.
  • Often seen in younger dogs, they are best treated with surgical removal.
  • There are other types of benign tumors as well, but Dr. St-Vincent warns, “Even the benign tumors are cause for concern because some can transform into cancerous tumors, or, although benign, can be just as invasive to the surrounding tissues and cause destruction of the nose and facial structures, leading to difficulty breathing and poor quality of life, just like the more common malignant nasal tumors.” (AKC)

There Are Several Different Types of Nose Cancer in Dogs (Dog Cancer.com)

There are a variety of different cancer types that can occur in the nasal cavity, so in this article, we are taking a broad view of nose cancer in dogs.

• Nearly two-thirds of nasal tumors in dogs are carcinomas, including adenocarcinoma, squamous cell carcinoma, and undifferentiated carcinoma.
• The bulk of the remaining tumors are sarcomas, including fibrosarcoma, chondrosarcoma, osteosarcoma, and undifferentiated sarcoma.

Please note that you may see links to other articles that go more in-depth on the less common types of canine nose cancer.

Adenocarcinoma, the Most Common Canine Nose Cancer

• Adenocarcinoma is the most common nasal tumor in dogs. 
• Overall, adenocarcinomas respond better to radiation therapy than squamous cell carcinoma or undifferentiated carcinoma and have a relatively better long-term prognosis.

Squamous Cell Carcinoma

• Squamous cell carcinoma may involve the nasal planum or other sites covered with squamous epithelium, such as the gums, tonsils, or tongue.
• It can also originate from the mucosal lining of the frontal sinus and nasal passage.
• Historically, dogs with squamous cell carcinoma don’t respond as well to radiation as dogs with sarcomas or adenocarcinomas do.

Undifferentiated Carcinoma

• Undifferentiated carcinoma translates to “undifferentiated tumor.” This refers to a tumor with little or no evidence of differentiation, meaning it does not resemble normal tissue.
• Nasal undifferentiated carcinoma is believed to originate from the Schneiderian epithelium (the membranous lining of the maxillary sinus cavity) or the nasal ectoderm of the paranasal sinuses.
• Given the undifferentiated nature of this malignancy, immunohistochemical analysis (see below) is constructive so your veterinarian can confidently formulate a treatment plan.
• Historically, dogs with undifferentiated carcinoma have a poorer outcome after radiation therapy than those with sarcomas or adenocarcinomas.

Chondrosarcoma

• Chondrosarcoma is a malignant tumor involving the cells that produce cartilage matrix (the stuff cartilage is made from).
• Dogs with intranasal chondrosarcomas may have better treatment responses than dogs with adenocarcinoma or squamous cell carcinoma.

Osteosarcoma

• Osteosarcoma is a malignant mesenchymal tumor and is the most common primary bone tumor in dogs. Osteosarcoma accounts for 6% of nasal tumors.

Undifferentiated Sarcoma

• Undifferentiated sarcoma is a type of soft tissue sarcoma, also called unclassified sarcoma.³⁰

Nose Cancer in Dogs Can Be Hard to Diagnose Accurately

• Nasal tumors often represent a diagnostic and therapeutic challenge due to their confined location within the nasal cavities.²
• It can be difficult to see them clearly because of the tight space and the complex nasal cavity structures. It can be challenging to treat them for the same reason. (Dog Cancer.com)