A variety of neoplastic lesions (benign and malignant) occur in the oral cavity. These can be odontogenic or non-odontogenic in origin. In addition, non-neoplastic lesions and swellings (e.g., gingival hyperplasia and infective conditions) can be confused with neoplasia. Conversely, oral neoplasms may present as nonhealing ulcerative lesions rather than as masses. Also, the so-called epulides (see below) constitute a variety of pathologic entities.
Malignant neoplasms of the mouth and pharynx constitute 5–7% of all canine tumors (Verstraete 1995). The most common malignant neoplasms are malignant melanoma (30–35%), squamous cell carcinoma (20–30%) and fibrosarcoma (1–20%) (Verstraete 1995). Osteosarcoma is also relatively common.
The term epulid (epulis) is a clinically descriptive term referring to a localized swelling on the gingiva. A number of distinct histopathologic entities can thus present as an epulis, including malignant tumors. However, most epulides are non-neoplastic lesions or odontogenic tumors. A study (Verstraete et al. 1992), found that 44% of epulides were focal fibrous hyperplasia. Peripheral odontogenic fibromas were also common (17%) and peripheral ameloblastoma accounted for 18% of epulides examined histologically.
Odontogenic tumors are benign neoplasms that arise from odontogenic tissue. They are classified based on the type of neoplastic tissue (epithelial or mesodermal) and whether they are inductive or non-inductive (i.e., whether an interaction similar to that seen during odontogenesis takes place between epithelial and mesenchymal tissues or not). The odontoma is an example of an inductive tumor and the peripheral ameloblastoma and the peripheral odontogenic fibroma are examples of non-inductive tumors.
Radiography, while not diagnostic of the tumor type, will provide information about the extent of bony involvement of oral neoplasms. Such information, in conjunction with the histopathologic diagnosis, is important in planning tumor management.
It is essential to determine if the presenting lesion is inflammatory or neoplastic and if it is neoplastic then whether it is a benign or malignant lesion. Biopsy and histopathological examination of a representative sample is the mainstay of managing oral neoplasia and should be the first step in the diagnostic workup. Excisional biopsy, often from several locations, will give the best likelihood of submitting representative material to the pathologist. The clinical findings and the histopathological diagnosis need to fit. The pathologist needs clinical information from you (i.e., animal signalment, location and clinical appearance of lesion, radiographic signs, etc.). It is useful to submit photos.
Once the histopathological diagnosis has been ascertained, then further diagnostic measures should be taken. If it is a benign neoplasm then excision is usually the next step. For malignant lesions further workup is required to be able to choose the best treatment strategy. The general health of the animal should be checked (full clinical examination, blood samples for haematology and biochemistry, urine analysis) and every effort should be made to get an accurate clinical staging (i.e., is there spread to regional lymph nodes, is there evidence of metastatic disease or paraneoplastic syndrome).
The histopathological diagnosis and the clinical staging will allow optimal treatment planning. Malignant oral neoplasms are best treated with surgical excision yielding clean margins. In some situations, radio- or chemotherapy may be appropriate.
In deciding the best treatment regimen the expected survival time and quality of life are important. The best situation is early detection with no evidence of local or distant spread and in a location where clean margins of appropriate width for the histological type can be achieved. There will be situations when malignant disease is widely disseminated and euthanasia is the most 'humane' option.