Cytology or biopsy
Any suspect nasal mass effect may be aspirated to provide a rapid preliminary cytologic diagnosis. However, fine-needle aspiration
is not always anatomically feasible because most nasal tumors are relatively inaccessible because of their location within
the nasal cavity. Occasionally, nasal tumors associated with marked bony lysis of the nasal bone, frontal sinus, or maxilla
may allow for direct disease extension outwards of the nasal cavity, resulting in a subcutaneous mass effect that may be sampled
easily with fine-needle aspiration.
More commonly, a definitive diagnosis of nasal neoplasia is achieved through biopsy techniques, which are considered to be
safe and only rarely induce unacceptable morbidity.31
Biopsy samples may be obtained by a variety of methods including
1. A Baker's punch biopsy of superficial facial deformities
2. Blind intranostril sample collection by using cup forceps or a bone curette
3. A rhinoscopy-assisted biopsy
4. An otoscopic illuminator-assisted biopsy of rostral lesions
5. An open-rhinotomy biopsy
6. Aggressive nasal flushing with subsequent dislodgement of tumor fragments
Figure 3. A ventral rhinotomy approach through the soft palate allows for the visualization and exposure of a relatively
small nasal carcinoma arising from the ventral meatus. (Image courtesy of Louis-Philippe de Lorimier, DVM, DACVIM [oncology].)
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Before biopsy, it is recommended to perform a CT scan to maximize the likelihood of obtaining a representative tissue sample
for definitive diagnosis. Although blind-biopsy techniques preclude direct visualization of suspect tumor masses, the relatively
narrow confines of the nasal cavity afford good chances for the retrieval of tissue samples of diagnostic quality. Relatively
noninvasive, direct-visualization techniques, such as rhinoscopy-assisted biopsy or otoscopic illuminator-assisted biopsy,
are also commonly used to obtain a definitive diagnosis; however, they may be limited to retrieving small and superficial
pieces of mass lesions.
When nondiagnostic specimens are obtained by using noninvasive techniques, a surgical technique may be required for definitive
diagnosis. Surgical approaches for obtaining diagnostic samples include either a dorsal or ventral approach to the nasal cavity
or an approach to the nasopharynx through the soft palate (Figure 3). If a surgical approach is required to obtain a biopsy, a CT scan—if not already performed—is highly recommended for optimal
surgical planning.
STAGING
Table 1: Adams Modified Staging System for Nasal Tumors*
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Staging of nasal tumors can be addressed through categorizing local invasiveness (Tables 1 & 2) and metastatic behavior (Table 2). Three-view thoracic radiography and fine-needle aspiration of regional lymph nodes will provide the information necessary
to determine the stage based on metastatic behavior. A CT scan will provide highly valuable information regarding local invasiveness
in staging and planning for surgery or radiation therapy. Fine-needle aspiration and cytologic examination of regional lymph
nodes provide not only a rapid screening test for the presence of regional metastasis but may also allow for histopathologic
categorization of the primary tumor (epithelial, mesenchymal, or other). The mandibular and retropharyngeal lymph nodes should
be palpated and aspirated to check for regional metastases. Irrespective of lymph node size or lateralization, cytologic examination
of aspirates from all draining lymph nodes should be performed to assess for micrometastases.
Table 2: W.H.O. Staging of Canine Nasosinal Tumors*
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In addition to lymph node assessment, consider three-view thoracic radiography to rule out the existence of distant metastasis.
At the time of nasal tumor diagnosis, radiographic findings in most dogs are usually unremarkable since the metastatic rate
for nasal tumors is low. However, thoracic radiography may still be recommended since the prognosis and treatment planning
will change if metastatic lung nodules or concurrent cardiac or pulmonary disease are present. To exemplify the impact of
clinical stage on prognosis, in one study of 64 dogs with nasal adenocarcinoma, patients initially presenting with confirmed
regional (lymph node) or distant (pulmonary parenchyma) metastases had substantially shorter survival times (109 days) than
dogs presenting with only localized disease had (393 days).11
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