Oral Neuroma in a Dog: A Case Report

A neuroma is a tangled, circumscribed, non-neoplastic mass of neuronal tissue formed after axonal injury and consists of a mixture of fibroblasts, Schwann cells and axons. Traumatic neuroma is the most commonly recognized neuroma lesion in humans and can occur at any site in the body where a nerve is traumatized. A 15-year-old female Miniature Pinscher was presented with periodontal disease. A lump on the right side of the face was found, corresponding to a solitary cylindrical mass on the mucosal surface of the lower lip. Dental radiographs showed no lysis of the mandibular bone. After an inconclusive cytological examination, the mass was surgically removed, fixed in 10% formalin, embedded in paraffin, and routinely stained for light microscopy. Macroscopically, a whitish, firm, filiform mass measuring 2.5 × 0.5 × 0.3 cm was found. Microscopically, the mass was poorly defined and consisted of spindle-shaped cells forming bands, bundles, and sometimes coiled structures, resembling nerves, surrounded by fibrosis. The cells were monomorphic, but an area of increased cellularity and nuclear atypia was observed. Mitotic figures, Verocay bodies, or Antoni A and B patterns were not found. The mass was surrounded by oral epithelium, mucinous glands, and skeletal muscle. There is much confusion in veterinary medicine regarding the nomenclature of peripheral nerve sheath tumors, that is, schwannomas, neurofibromas, perineuromas, traumatic neuroma, and malignant tumors of the peripheral nerve sheath. This lesion had histological features consistent with a neuroma, an unusual entity in the canine oral cavity.