Canine and feline nasal tumors
Primary tumors of the nasal cavity account for about 1% or 2% of all neoplasms in dogs.1,2 Of these neoplasms, about 80% have histologic characteristics of malignancy.1 In dogs, nasal neoplasms are regionally invasive with frequent expansile growth into the nasal passages, frontal sinuses, and cranial vault cavity; however, documented distant metastasis to the lungs or regional draining lymph nodes is uncommon upon initial presentation.3,4
Nasal tumors are less commonly diagnosed in cats than in dogs but, nonetheless, behave similarly to canine nasal tumors with regional invasion and a low metastatic rate.1 Lymphoma and carcinoma (adenocarcinoma, squamous cell carcinoma) are the most common types of nasal tumor diagnosed in cats.1,8-10Other less frequently diagnosed nasal malignancies that have been reported in dogs and cats include fibrosarcoma, mast cell tumor, transmissible venereal tumor, hemangiosarcoma, neuroendocrine carcinoma (olfactory neuroblastoma), peripheral nerve sheath tumor, fibrous histiocytoma, rhabdomyosarcoma, leiomyosarcoma, and melanoma.1,3,4 Benign tumors may also arise from the nasal cavity, including nasal polyps and fibromas, but they are not discussed in this review article.
Similar to other neoplastic conditions that predominantly arise in the geriatric population, nasal tumors most commonly affect middle-aged to older dogs and cats. The average age of onset for nasal carcinomas is reported to be 9 or 10 years, while the development of nasal sarcomas is reported to occur in slightly younger animals (7 or 8 years old).3,4,9,11-16
Although nasal tumors may be diagnosed in any dog breed, dolichocephalic and mesocephalic breeds are considered to be at an increased risk for developing nasal tumors.15-18 One potential hypothesis for this observed breed predilection is that the greater nasal passage surface area in dolichocephalic and mesocephalic dogs predisposes them to greater exposure to inhaled carcinogens and subsequent tumor development. In addition, the larger nasal surface area would be associated with a greater number of nasal epithelial cells, which could be malignantly transformed after exposure to inhaled carcinogens.
Reports vary on whether there is a male sex predilection for nasal tumors in dogs. As such, it is unlikely that the development of nasal tumors is under hormonal influence. Contrary to dogs, male cats have been reported to have about a twofold increased risk for developing nasal tumors, although an underlying mechanism to explain this observation has yet to be postulated.1