The oral cavity is the fourth most common site for neoplasms in small animals (Pippi; Gomes, 2016), accounting for approximately 10% of tumors in felines, of which 90% are malignant (Bilgic et al., 2015). Squamous cell carcinoma (SCC) is a malignant epithelial neoplasm arising from keratinocytes (Rosolem et al., 2012) and is the most frequent oral malignancy in cats, representing 60-73% of malignant oral tumors (Beatty et al., 2000).

The etiology of SCC is multifactorial and not yet fully elucidated; however, exogenous factors such as prior non-malignant lesions, ingestion of canned foods, and chronic exposure to ultraviolet light are believed to predispose to its development (Daleck et al., 2016). Higher incidence has been reported in felines aged 9 to 14 years, in immunosuppressed animals, and in those with white or light-colored coats, with no sex or breed predisposition (Rosolem et al., 2012).

The sites most commonly affected by oral SCC in felines include the sublingual and lingual regions, maxilla, mandible, buccal mucosa, lip, and the caudal region of the pharynx and tonsils. Feline oral SCC shows a low metastatic rate to regional lymph nodes and, more rarely, to the lungs (Bilgic et al., 2015).

Clinical signs in felines with oral SCC include hyporexia, anorexia, weight loss, ptyalism, impaired or reduced grooming, halitosis, oral bleeding, dysphagia, exophthalmos, regional lymphadenomegaly, nasal obstruction, and tooth loss (Pippi; Gomes, 2016).

In most cases, the diagnosis of oral SCC can be presumptively established through cytological examination (Bonfanti et al., 2015). Cytology typically reveals epithelial cells with marked cellular pleomorphism, anisocytosis, anisokaryosis, and a high nucleus-to-cytoplasm ratio (Peteleiro et al., 2011).

Definitive diagnosis is achieved through histopathological analysis of the tissue (Pignone et al., 2012), which demonstrates neoplastic squamous epithelial cells arranged in cords and islands, with evident pleomorphism, prominent desmosomes, and occasional keratin pearl formation, associated with varying degrees of inflammation, necrosis, ulceration, and desmoplasia (Martin et al., 2010).

Imaging of the primary tumor is essential for assessing tumor location, degree of invasion, and surgical planning. Imaging modalities include radiography, computed tomography, and magnetic resonance imaging. Radiographs are useful for determining the extent of bone involvement. In feline oral SCC, radiographic findings may include osteolysis, periosteal proliferation, and dental resorption (Bilgic et al., 2015).

Maxillary lesions that invade bone tissue cause marked osteolysis and crater-like lesions due to destruction of the palatine process of the maxilla, incisive bone, and zygomatic arch, and may also exhibit areas of bone proliferation. Oral SCC affecting the mandibular region shows evidence of sunburst-like periosteal proliferation, bone lysis, and, in some cases, pathological fractures (Bilgic et al., 2015). It is estimated that a 30-50% change in bone mineral content is required before bone loss becomes radiographically detectable (Langland et al., 2002).

Once the diagnosis of oral SCC is established, treatment may involve surgery, chemotherapy, radiotherapy, or a combination of these modalities (Pippi; Gomes, 2016).

Early diagnosis plays a crucial role in prognosis, as outcomes vary according to tumor location and the severity of the condition at the time of diagnosis (Gayer, 2006).

The aim of the present study is to describe the radiographic, cytopathological, and histopathological findings in a domestic feline diagnosed with oral squamous cell carcinoma.

A female domestic shorthair cat (mixed breed), weighing 2.3 kg and aged six years, was examined at the Veterinary Center of the Octávio Bastos Foundation University Center (UNIFEOB), São João da Boa Vista, São Paulo, Brazil.

The animal presented with facial swelling, hyporexia, apathy, and a history of having undergone an oral prophylaxis surgical procedure with dental extractions performed by another professional, who had diagnosed the condition as feline gingivostomatitis complex.

On physical examination, vital parameters were within normal limits. Mild dehydration, normochromic mucous membranes, a cachectic general condition, absence of reactive lymph nodes, and bilaterally dry, opaque eyes with discharge were observed. The facial swelling extended from the mandibular region to the right lateral maxillary region. Intraoral examination revealed an ulcerative, hyperemic mass in the cheek region.

The animal was referred to the Complementary Propaedeutics sector for cranial radiography under sedation. Imaging revealed a mixed bone lesion with marked areas of lysis and bone proliferation, loss of trabecular pattern throughout the cranial bones, with greater involvement of the right hemiface. An extensive lytic area was noted in the zygomatic arch, maxilla, and nasal cavities, along with absence of dental elements in the right maxilla and increased soft tissue volume in the dorsal and right lateral regions of the skull (Figure 1).

Figure 1

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The clinical signs observed in the animal described in this case report consisted primarily of facial swelling extending from the mandibular region to the right maxilla, sites that are commonly reported in cases of oral squamous cell carcinoma (Bilgic et al., 2015).

In the present case, radiographic examination proved to be of critical importance for assessing lesion location, degree of invasion, and the extent of bone involvement. Reactive processes and bone destruction, as well as soft tissue edema, were identified-findings that are consistent with neoplastic processes or osteomyelitis (Kealy et al., 2010).

Cytological analysis revealed the presence of neoplastic epithelial cells, suggesting a presumptive diagnosis of squamous cell carcinoma (SCC). This interpretation was based on the observation of features such as marked cellular pleomorphism, anisocytosis, and anisokaryosis (Peteleiro et al., 2011), in addition to typical cellular morphologies, including rounded, angular, and tadpole-shaped forms, which are frequently associated with SCC (Barger; Macneill, 2017).

Histological findings, including neoplastic epithelial cells arranged in islands, necrosis, and bone invasion, are commonly observed in cases of SCC. These lesions may also present occasional keratin pearls, prominent desmosomes, and varying degrees of inflammation and desmoplasia (Martin et al., 2010).

Based on the cytological and histological findings, in association with the radiographic signs, a definitive diagnosis of oral squamous cell carcinoma was established.

Radiographic examination played a fundamental role in the identification and evaluation of the characteristics of bone lesions associated with oral squamous cell carcinoma. Cytological analysis complemented the radiographic findings, leading to a presumptive diagnosis that was subsequently confirmed by histological evaluation.

These results highlight the importance of combining diagnostic approaches to ensure diagnostic accuracy and to support the most appropriate therapeutic decision-making.