Flea control collars
In one study, cats that wore flea collars had a statistically significant fivefold increased risk of developing oral squamous
cell carcinoma when compared with control cats.7 This increased risk was possibly due to the proximity of the collar pesticides to the oral cavity.7 The use of flea shampoos, however, was associated with a 90% reduction in the risk of developing oral squamous cell carcinoma.
This finding may be associated with regular shampooing causing a decrease of chemical contaminants on the coat and, thus,
decreased oral intake of chemicals by the cats through grooming.7
The same study that evaluated passive smoke exposure also revealed a statistically significant threefold increase in oral
squamous cell carcinoma in cats that frequently ate canned cat food when compared with those eating dry food.7 Additionally, cats that ate canned tuna had a statistically significant five-time higher risk for oral squamous cell carcinoma
tumor development when compared with cats that did not consume canned tuna.7 The increase could be related to differences in the nutrient content of these foods. Another explanation for the difference
in risk among food types may be that cats eating dry food have less tartar buildup and, thus, better oral hygiene than those
that eat canned food.4
DIAGNOSIS AND STAGING
History and physical examination
A thorough history and complete physical examination are the first steps in assessing potential cancer patients. Ask questions
regarding the duration and progression of the clinical signs. Many cats with oral squamous cell carcinoma exhibit some or
all of the following clinical signs: inappetence, anorexia, weight loss, incessant chewing, halitosis, or excessive salivation.2 When examining cats with these clinical signs, it is imperative to perform an oral examination. Palpate the maxilla and
mandible for any evidence of swelling or pain. Thoroughly examine the gingiva, buccal and pharyngeal mucosa, palate, and sublingual
regions for masses. An ulcerated, red, locally invasive lesion is highly suggestive of an oral tumor (Figure 5). It is important to characterize the abnormal findings including the size, location, and number of lesions. Assess the lesion
for ulceration, necrosis, and invasion of adjacent bony structures, which is often suspected if one or more loose teeth are
found at the site.
Figure 5. Note the small, round, raised, ulcerated mass on the palatal mucosa; biopsy confirmed squamous cell carcinoma.
Differential diagnoses in cats with oral masses include dental disease, malignant tumors, benign abnormalities, and infections
(Table 1). Squamous cell carcinoma is the most common malignant oral tumor in cats, accounting for 60% of such tumors.1 Fibrosarcoma is the second most common malignant oral tumor, with lymphoma, melanoma, adenocarcinoma, chondrosarcoma, granular
cell tumors, fibropapilloma, hemangiosarcoma, osteosarcoma, and mast cell tumors occurring less frequently.1,6,9 Ameloblastomas have also been reported in cats and have been confused with two other odontogenic tumors: the inductive fibroameloblastomas
(or feline inductive odontogenic tumors) and the calcifying epithelial odontogenic tumors (or amyloid-producing odontogenic
tumors).10 Benign masses that may occur in the feline oral cavity include osteoid osteoma, fibromatous epulis, gingival hyperplasia,
nasopharyngeal polyps, and eosinophilic granulomas.1,6,9 Infectious causes of oral masses include cryptococcosis, blastomycosis, and actinomycosis.
Table 1 Differential Diagnoses in Cats with Oral Masses and Maxillary or Mandibular Swelling
A one-year prospective study in which 24 cats presented for evaluation of mandibular swellings revealed that 12 of the cats
had malignant tumors while the other 12 cats had benign lesions.9 The malignant tumors included eight squamous cell carcinomas, two lymphomas, one melanoma, and one adenocarcinoma.9 Almost all the nonmalignant swellings in this study were caused by osteomyelitis secondary to dental disease, such as end-stage
odontoclastic resorptive lesions, severe periodontal disease, and endodontic disease secondary to chronic pulpal exposure
associated with canine tooth fractures. Clinical and radiographic findings could not differentiate benign from malignant mandibular
lesions.9 Thus, a biopsy is crucial for obtaining an accurate diagnosis.