Nasal Tumors in Dogs and Cats
Nasal tumors in pets are relatively uncommon, accounting for only 1% of all cancers in dogs. However, they are the most common tumors found along the respiratory tract, responsible for around 60-80% of reported respiratory tumor cases in dogs and cats. Since nasal tumors have an increased tendency to be malignant, early detection and treatment are vital in preventing serious complications associated with the condition. However, nasal tumors are also arguably one of the most overlooked tumor diagnoses in both dogs and cats because of their vague symptoms. Keep reading to learn more.
Types of Nasal Tumors in Dogs and Cats
These tumors are considered locally invasive especially in dogs. They’re commonly seen growing on the surface of the nasal passages and can extend into the frontal sinuses and cranial cavity. There have been reported cases of nasal tumors spreading to the lungs and regional lymph nodes, though quite uncommon.
The most common type of nasal tumor seen in dogs is carcinoma. They comprise around 60-78% of all reported nasal tumors in dogs and are categorized into different subtypes based on histological characteristics. The most common subtype of nasal carcinoma reported in dogs is adenocarcinoma, which accounts for 45% of nasal tumor cases. This is followed by squamous cell carcinoma, chondrosarcoma, undifferentiated carcinoma, and unspecified nasal carcinoma.
In cats, carcinoma (adenocarcinoma and squamous cell carcinoma being the most common) and lymphomas are the most common types of nasal tumors diagnosed. Other less common nasal tumors diagnosed in both dogs and cats include transmissible venereal tumor, fibrosarcoma, mast cell tumor, fibrous histiocytoma, hemangiosarcoma, and melanoma.
Benign tumors like inflammatory polyps and fibromas may also grow along the surface of the nasal passages of dogs and cats. These tumors are not usually invasive, and their growth rarely extends from the point of origin, but they can grow in size significantly to cause serious complications for the animal.
Are certain breeds prone to nasal tumors and cancer?
Nasal tumors are considered diseases of older animals, and similar to most neoplastic diseases, it commonly affects middle-aged to older dogs and cats. Nasal carcinomas are commonly seen in animals around 9 to 10 years of age, while nasal sarcomas tend to develop in younger animals around 7 or 8 years of age.
Breeds that are commonly affected with nasal tumors are those that have elongated nasal passages. One hypothesis is that the risks of nasal tumor development are greater in breeds with a high nasal surface area due to the increased number of epithelial cells. There has been no reported sex predilection in both dogs and cats.
In some studies, animals that are regularly exposed to environmental carcinogens such as tobacco smoke have been shown to have an increased risk of developing nasal tumors as they get older. However, the relationship between exposure to a carcinogen and nasal tumor growth is still debatable due to the very few studies that have been performed.
Symptoms of Nasal Tumors in Dogs and Cats
Part of the reason why nasal tumors tend to be overlooked and are diagnosed later than most tumors is because of the vague clinical signs associated with them. Due to their location, symptoms of nasal tumor development in dogs and cats mimic most respiratory problems. Veterinarians and pet owners tend to treat common respiratory problems first and only consider the possibility of nasal tumor growth under certain circumstances.
The most common symptoms seen in dogs and cats with nasal tumors include nasal discharge, excessive sneezing, and nose bleeding (epistaxis). In some cases, facial asymmetry may be observed, especially if the tumor is locally aggressive and invasive. Breathing difficulties are seen in dogs and cats with nasal tumors that partially or fully obstruct the nasal passages.
Because of the close proximity of the nasal passages to the eyes and the aggressive nature of nasal tumors, affected animals can exhibit signs of ocular disease such as eye discharge, conjunctivitis, and eye protrusion (exophthalmos).
Severe cases of nasal tumors tend to cause significant facial deformity in dogs and cats. Neurologic signs and enlargement of certain lymph nodes can be observed in animals with nasal tumors that have invaded nearby tissues. The presence of facial deformity can be highly suggestive of the metastatic nature of the tumor. Systemic signs of illness such as decreased appetite, lethargy, and progressive weight loss are also commonly observed in dogs and cats with advanced stages of nasal tumor growth.
Diagnostic Tests for Nasal Tumors in Cats and Dogs
As mentioned, since nasal tumors share similar clinical signs with most common respiratory problems, diagnosis is often overlooked unless physical manifestation is evident enough (i.e. presence of facial deformity). A thorough physical exam is needed to help determine if further investigation is needed in dogs and cats showing symptoms of respiratory disease.
Diagnostic imaging is the most effective means to confirm the presence of tumors or growths along the nasal passages of cats and dogs. Radiographs (x-rays) can help identify the presence of nasal tumors, but more advanced imaging such as MRI or CT scan not only confirms the presence of a tumor but can also give you and your vet a clearer picture of the extent of growth and if it has invaded nearby tissues.
Chest x-rays can also check for possible metastasis (spread of cancer) and are usually performed in pets with a confirmed nasal cancer diagnosis. Definitive diagnosis will come from histopathology of tumors samples. Obtaining a biopsy sample for histopathology can be done in different ways. Rhinoscopy-assisted biopsy provides an effective and non-invasive way to obtain tumor samples, but surgical procedures may be necessary for tumors located at the back of the nasal passages.
If your dog or cat is showing signs of an upper respiratory problem that won’t go away, it’s best to visit your vet to rule out the possibility of nasal tumors.
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