Clinical signs in animals with an oral mass can vary. The patient may present after an owner has identified a mass. If the
mass is small or in the caudal aspect of the oral cavity, it may not be noted by the owner and may be found on routine physical
examination. Clinical signs other than an oral mass that the owner may report include apparent inappetence or reluctance to
eat, dysphagia, ptyalism, halitosis, or hemorrhage from the oral cavity. Loss of a tooth, loose teeth, or recent history of
a dental procedure with removal of several teeth should also prompt further oral evaluation.
DIAGNOSTIC APPROACH AND STAGING
Once an oral mass has been identified, a general health screening, including a complete blood cell count, serum chemistry
profile, and urinalysis, is appropriate since many patients affected by oral tumors are older and may have concurrent diseases.
Additional diagnostic tests, such as lymph node cytology, thoracic imaging, biopsy of the mass, abdominal ultrasonography,
and skull and dental radiography, can help you diagnose the tumor type as well as determine the stage of disease by identifying
metastasis (Table 1).
World Health Organization Staging for Tumors of the Oral Cavity*
Lymph node cytology
Fine-needle aspiration and cytologic examination of the mandibular lymph nodes is a quick and easy test to screen for local
metastasis. Ideally, both lymph nodes are aspirated since rostral tumors and tumors that cross midline (which may be difficult
to detect in some patients) will drain bilaterally. Metastatic cells found in the lymph node not only may offer prognostic
information but can also help identify the primary tumor.
A recent study that evaluated 100 dogs with oral melanoma determined that lymph node size and palpation cannot be relied on
to accurately determine whether disease is present within that lymph node.31 Forty-seven percent of the cases had no cytologic or histologic evidence of metastasis, of which 23 dogs (49%) had enlarged
lymph nodes. Conversely, and importantly, 16 of 40 dogs (40%) with lymph nodes that were thought to be normal on palpation
did have cytologic or histologic evidence of metastatic disease.31 In another study involving seven cats and 37 dogs with a variety of solid tumors, six out of 27 (22%) of the animals in
which lymph nodes were normal-size or only slightly enlarged had metastatic disease identified cytologically.32 The sensitivity of cytologic evaluation of fine-needle aspirates was 100%, and the specificity was 96%, signifying that
fine-needle aspiration is a consistent method of assessing the regional lymph nodes.32
Keep in mind that other lymph nodes such as the retropharyngeal and parotid lymph nodes drain the oral cavity and cannot be
palpated on examination. These lymph nodes may be affected and are hard to evaluate. Computed tomography (CT) may help in
visualizing these lymph nodes, if clinically indicated.33