Oral tumours account for approximately 6% of all neoplasia in dogs, with about 70% being malignant. Melanoma is the most common, followed by squamous cell carcinoma and fibrosarcoma. While less frequent, oral tumours tend to be more aggressive in cats. Squamous cell carcinoma is the most common, accounting for up to 70% of oral cancers in cats. The prognosis for many oral cancers significantly improves when diagnosed in the early stages. For example, dogs with early- stage oral melanomas treated with surgery alone have a median survival time of about 17-18 months, compared to only 3-4 months for advanced cases. Similarly, early detection of feline oral squamous cell carcinoma can increase the median survival time from 2-4 months to potentially over a year with appropriate treatment.

Early diagnosis enables more treatment options, including the potential for complete surgical removal, which can be curative in most cases. It also lowers the risk of cancer spreading and enhances the effectiveness of additional treatments like radiation or chemotherapy. Early diagnosis of malignant oral tumours requires a comprehensive approach, including clinical examination, advanced imaging techniques, histopathological analysis, and tumour staging. The diagnostic process typically begins with a comprehensive examination of the oral cavity to identify abnormalities such as masses, ulcerations, or textural changes in oral tissues. This initial assessment guides the subsequent diagnostic steps.

Intraoral X-rays allow visualisation of bone involvement and density changes. Advanced modalities like computed tomography (CBCT-CT) and magnetic resonance imaging (MRI) provide 3D assessment of tumour extent and invasion into adjacent structures. Biopsy techniques are indispensable for definitive diagnosis. Fine needle aspiration (FNA) provides a minimally invasive method for cytological examination. When FNA yields inconclusive results, an incisional biopsy is necessary for comprehensive histopathological analysis. Histopathology can confirm malignancy and provide critical information on tumour type, grade and characteristics that inform treatment strategies.

Immunohistochemistry (IHC) is a technique that helps identify specific proteins expressed by tumour cells. It identifies the cell type from which the tumour originated, and can detect early malignant transformation before visible changes occur. It can also detect markers associated with an increased risk of metastasis and help select appropriate treatments based on tumour markers. Some IHC markers provide valuable prognostic information by offering insight into probable tumour behaviour. Importantly, IHC allows for the extraction of maximum information from limited sample sizes, which is very helpful when dealing with small biopsies. Ultrasonography, while not typically a primary diagnostic tool for oral tumours, allows for evaluating regional lymph nodes for potential metastatic involvement. It enables the assessment of lymph node size, shape, internal architecture, and vascularity. Doppler ultrasound can detect increased blood flow, often associated with malignancy. However, ultrasound has limitations in detecting small or deep-seated metastases, necessitating a multimodal diagnostic approach.

In conclusion, comprehensive oral examinations during veterinary consultations and regular dental check-ups are the key to the early detection of oral tumours in dogs and cats. Pet owners are often unaware of the problem until the tumour has advanced, resulting in visible swelling, difficulty eating, bleeding, or other noticeable symptoms.

References
- Cray M, Selmic LE, Ruple A. Demographics of dogs and cats with oral tumors presenting to teaching hospitals: 1996-2017. J Vet Sci. 2020 Sep;21(5):e70.
- WHO Classification of Tumours Editorial Board. Head and Neck tumours. Lyon (France): International Agency for Research on Cancer; 2022. https://publications.iarc.fr/. - Kim WS, Vinayak A, Powers B. Comparative Review of Malignant Melanoma and Histologically Well-Differentiated Melanocytic Neoplasm in the Oral Cavity of Dogs. Vet Sci. 2021 Nov 2;8(11):261.
 - Soltero-Rivera, M.M., Krick, E.L., Reiter, A.M., Brown, D.C., & Lewis, J.R. Prevalence of regional and distant metastasis in cats with advanced oral squamous cell carcinoma: 49 cases (2005-2011). Journal of Feline Medicine and Surgery, 2014 16(2), 164-169.
- Maekawa N, Konnai S, Okagawa T, Nishimori A, Ikebuchi R, Izumi Y, et al. (2016) Immunohistochemical Analysis of PD-L1 Expression in Canine Malignant Cancers and PD-1 Expression on Lymphocytes in Canine Oral Melanoma. PLoS ONE 11(6): e0157176.
 - de Bondt, R.B.J. et al. Detection of lymph node metastases in head and neck cancer: A meta-analysis comparing US, USgFNAC, CT and MR imaging. European Journal of Radiology, 64(2), 266-272