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A diffuse traumatic neuroma in the palate: a case report
© Eguchi et al. 2016
Received: 7 January 2016
Accepted: 25 April 2016
Published: 11 May 2016
A traumatic neuroma is not a true neoplasm but a reactive proliferation of neural tissue that commonly occurs after the transection or damage of a nerve bundle. Traumatic neuromas are rare in the oral region and usually occur as a solitary nodule of the mental foramen, lower lip, or tongue. This is the first report of a diffuse traumatic neuroma of the palate.
A 30-year-old Japanese man was referred to our clinic complaining of painful swelling of the left side of his palate. The swelling was diffuse and his pain increased with palpation of his palate. He had no noteworthy medical or family history, and was not aware of any history of trauma or inflammation in his head or neck area. We administered antibiotics and non-steroidal anti-inflammatory drugs because we suspected that his symptoms were the result of inflammation caused by an infection. However, his symptoms did not change. An incisional biopsy was performed, and histopathologic examination indicated that the lesion was a traumatic neuroma. Under general anesthesia the lesion was resected with a 5-mm margin using an electric scalpel because of the diffuse expansion and indistinct borders of the mass. Some tumor cells were observed within the surgical margins of the resected specimen, but there has been no recurrence of either the pain or mass in the 3 years since the surgery.
The location and diffuse nature of this traumatic neuroma are both very rare. While we were initially unsure about the diagnosis and treatment of this mass, the treatment outcome has been good. However, a postoperative recurrence can occur at any time following the excision of a traumatic neuroma, and close long-term follow-up will continue.
A traumatic neuroma is a hyperplastic lesion caused by trauma or surgery that involves the peripheral nerves and is not considered to be a true neoplasm . It may occur in any part of the body, including the head, neck, gallbladder and thigh . The clinical features of a traumatic neuroma include the formation of a solitary nodule less than 2 cm in diameter, neuralgic pain, tenderness, paresthesias and increased pain on palpation over the lesion [2, 3]. The recommended treatment of a traumatic neuroma is simple excision rather than nerve resection or alcohol blocks . In the oral region, a traumatic neuroma is a rare disorder that occurs most commonly at the mental foramen, lower lip, tongue and intra-osseous areas [4, 5]. It is extremely rare in the palate. There have been no previously published reports of a diffuse traumatic neuroma. Here we describe the treatment outcomes of an unusual diffuse traumatic neuroma occurring in the palate.
Traumatic neuromas, also called amputation neuromas, are not true neoplasms but reactive proliferations of neural tissue that occur after transection or damage to a nerve bundle. Jones and Franklin  reported that the frequency of traumatic neuromas was 0.34 % in the oral region. The most common sites for a traumatic neuroma in the head and neck are the inferior alveolar nerve, lingual nerve, and great auricular nerve . There have been few reports of traumatic neuromas in the palate.
Clinical and histopathological differential diagnosis of traumatic neuroma versus other neurogenic tumors
Symptomatic (anesthesia, dysesthesia, and pain), solitary
Many nerve bundles, fibrous connective tissue background containing inflammatory cells
Asymptomatic, typically multiple, associated with multiple endocrine neoplasia type 2B
Many nerve bundles, normal or loose fibrous connective tissue background without inflammatory cells
Asymptomatic, solitary, or multiple
Nuclei with wavy or serpiginous prolife, fibrous connective tissue background containing mast cells
Circumscribe, spindle cells showing palisading arrangement
Many nerve bundles containing vessels, fibrous connective tissue background without inflammatory cells
The palatine mucosa is composed of a keratinized stratified squamous epithelium, lamina propria, and a submucosal layer. The submucosal layer is composed of glandular and adipose tissues that surround the palatine neurovascular bundle that runs under the lamina propria . The palatine mucosa is innervated by the nasopalatine nerve and the greater palatine nerve. The nasopalatine nerve is a branch of the sphenopalatine nerve, and innervates the palatal tissues and gingiva anterior to the canines after passing through the incisive canal . The greater palatine nerve is the anterior branch of the palatine nerve, and innervates the palatal tissues and gingiva posterior to the canines after passing through the greater palatine foramen . Both nerves are sensory nerves, and a traumatic neuroma commonly occurs in sensory nerves . In our patient, a traumatic neuroma developed in the left side of the palatine mucosa of his molar region, and his pain was limited to his posterior palatal gingiva. His greater palatine nerve was not cut, and histopathologic examination revealed that the trunk of his greater palatine nerve had no pathologic changes. Based on those findings, the origin of his neuroma was thought to be a branch of his left greater palatine nerve.
Causal factors for oral traumatic neuromas include tooth extraction, orthognathic surgery, ill-fitting dentures and intra-oral incisions [1, 3, 14]. In our case, however, there was no history of trauma or surgery according to the patient. However, the palatine mucosa is easily injured by burns and mechanical trauma during eating, resulting in a compounded thermal and mechanical trauma . As this patient’s traumatic neuroma was diffusely expanded within the palate, it may have been induced by a broader nerve injury such as a burn.
It is a possibility that our surgical treatment did not result in the complete excision of the lesion. However, the tumor has not recurred in the 3 years since the surgery. Tay et al.  reported that monopolar diathermy reduces the rate of neuroma formation, and electrical coagulation of the proximal nerve stump can prevent the development of neuromas . Simple excision is therefore highly recommended in the treatment of traumatic neuromas .
The borders of diffuse traumatic neuromas are often unclear, and the extent of the actual tumor may be such that a complete excision would result in severe neurologic damage, such as an area of hypoesthesia or complete nerve palsy. In these cases, simple excision of the tumor using an electrical scalpel is an effective method of treatment, and reduces the likelihood that the residual traumatic neuroma tissue would cause repeat symptoms or a full recurrence of the tumor.
We report an extremely rare traumatic neuroma in an uncommon location and without a defined cause.
Written informed consent was obtained from the patient for the publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
The authors thank the medical technologist Tomoya Kato, who performed all immunohistochemical staining.
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