‘other’ Oral Tumors

Oral tumors are common in dogs and cats. They may be of dental (odontogenic) or non dental origin. The most common malignant oral tumors in dogs are malignant melanoma, squamous cell carcinoma and fibrosarcoma, while the most common oral tumors in the cats are squamous cell carcinoma and fibrosarcoma. Less common malignant tumors occur in the oral cavity of dogs include osteosarcoma, multilobular tumor of bone, tonsillar lymphoma and squamous cell carcinoma, epitheliotropic T-cell lymphoma (mycosis fungoides), histiocytic sarcoma and plasmacytomas. Odontogenic tumors originate from the tooth forming structures and include peripheral odontogenic tumors, acanthomatous ameloblastoma, odontoma, dentigerous cyst and feline inductive odontogenic tumors. Although generally considered benign they can be locally aggressive. Oral osteosarcoma is the fourth most common oral tumor in dogs and affects the mandible and less often the maxilla. Regional and distant metastasis are less common than for appendicular osteosarcoma. Multilobular osteochrondrosarcoma (multilobular tumor of bone) is a variant of osteosarcoma affecting the cranium, orbit, zygomatic arch, palate, maxilla and mandible. It may be palpable as a firm, fixed mass. Patients may exhibit pain upon opening of the mouth if the mandible or zygomatic arch are involved. Radiographs show a popcorn appearance with stippled and heavily calcified regions. Computed tomography is indicated to detect the extent of tumor involvement in the surrounding bone and soft tissues. Prognostic factors for local recurrence and metastatic rate are dependent upon surgical margins and histologic grade. Epitheliotropic T-cell lymphoma (mycosis fungoides) occurs in older dogs with a possible over representation of cockers and poodles. Lesions in the oral mucosa may show primarily a mucocutaneous junction distribution or may be solitary. Depigmentation of the affected area is common. This variant still has the potential to spread systemically, although it may be many months before other lymphoma is clinically apparent. Tonsillar squamous cell carcinoma is considerably more aggressive than either gingival or lingual squamous cell carcinoma. It occurs in dogs with a median age of 9-11 years. It has a high rate of metastasis early in the disease process. Treatment is surgical excision in combination with radiation and chemotherapy. Extramedullary plasma cell tumors appear as smooth, pink to red, raised, well circumscribed nodules. Plasmacytomas of the oral mucosa are rarely associated with systemic disease. Surgical excision is most often curative. Odontogenic tumors originate from the tooth forming structures (epithelial or mesenchymal dental structures). Peripheral odontogenic fibromas were previously described as fibromatous and ossifying epulides. They are benign, slow growing, non invasive, firm, smooth, pink masses that originate at the gingival sulcus from periodontal ligament stroma. Radiographs show no changes in the underlying alveolar bone structure. The ossifying type of peripheral odontogenic fibroma contains varying amounts of calcified tissue within the tumor. Treatment for these tumors is local excision or excision of the mass in combination with extraction of the associated tooth.