Tumors of the nasal cavity and paranasal sinuses account for 1% to 2% of all canine neoplasms. The classic staging system proposed by the World Health Organization (WHO) uses tumor size, regional lymph node involvement, and distant metastasis, and is based on radiography findings. Computed tomography (CT) can delineate lesions more accurately, but there are no reports on staging of nasal/paranasal tumors using CT. A retrospective study examined records of 112 dogs with histologically confirmed nasal tumors that had undergone radiography and CT. A staging system based on CT findings was defined and the difference in survival time according to each staging system was examined. Results showed dogs classified under WHO stage II generally lived longer than those classified under WHO stage III. Patients classified under WHO stage III had various levels of tumor progression, and when these patients were further grouped under CT stages III and IV, the CT stage III patients lived significantly longer than CT stage IV patients. CT stage III patients also had significantly longer survival times when treated with a combination of surgery and radiation when compared to untreated dogs in CT stage III. There was no significant difference in survival times between different treatment modalities for dogs in CT stage IV. The results suggest that dogs in WHO stage III have various levels of tumor progression, so CT staging may be more accurate and helpful in estimating prognoses of dogs in later stages.

COMMENTARY: The anatomy of the head is very complex, making it difficult to determine how extensive a mass is with plain-film radiographs. In our clinic, we use contrast-enhanced CT exclusively to evaluate the extent and invasiveness of canine nasal tumors. Whether the mass is unilateral or bilateral, boney lysis, facial deformity, cribriform plate involvement, and lymph node enlargement are important findings that are easily detected with CT. The scans can then be used for surgery and/or radiation planning. Although it is still not clear whether surgery, radiation, chemotherapy or a combination of these is the best way to treat nasal tumors, contrast-enhanced CT gives the veterinarian and client an enormous amount of information for a reasonable price. With the increasing availability of CT in private specialty practices, we highly recommend this type of imaging over plain-film radiographs for assessment of canine nasal tumors.

Prognosis of canine patients with nasal tumors according to modified clinical stages based on computed tomography: A retrospective study. Kondo Y, Matsunaga S, Mochizuki M, et al. J VET MED SCI 70:207-212, 2008.