Neurofibroma of the hard palate

Abstract

Neurofibromas are defined as benign tumours arising from peripheral nerve sheaths. Few intraoral palatal cases have been reported. Neurofibromas can occur as part of neurofibromatosis, type 1 (NF1) or type 2 (NF2). A 41-year-old patient presented with a slowly enlarging soft tissue mass on the hard palate. An incisional biopsy was performed, which confirmed the diagnosis of a neurofibroma associated with NF1. It should be considered that there is a chance of malignant transformation. Here, we discuss the clinical features, types, diagnosis, histopathology and treatment options.

Background

Neurofibromatosis type 1 (NF1) has an estimated incidence of 1/3000 in the worldwide population and is an autosomal dominant condition.¹

A neurofibroma is defined as a benign tumour of the peripheral nerve sheath. They have mixed cellular components; Schwann cells, perineurial hybrid cells and intraneural fibroblasts. Patients with NF1 have an increased risk of developing malignant tumours, in particular, transformation to malignant peripheral nerve sheath tumours.²

More recently, oral manifestations associated with NF1 have demonstrated a dramatically increased prevalence from 4%–7% to 66%–72%.³

Case presentation

We report a case of a neurofibroma of the hard palate.

A 41-year-old male patient was referred to the Mid Yorkshire Hospital Maxillofacial Outpatient Department by a general dental practitioner for investigation of a swelling on the hard palate. The patient reported a 4-month history of a slowly enlarging mass on the hard palate. There was no pain associated with the lesion and it was asymptomatic.

The patient has NF1, scoliosis, renal artery stenosis and hypertension. There is no family history of NF.

Socially, he is a non-smoker and drinks around 10 units of alcohol per week.

On examination, the patient has multiple skin-coloured nodular masses on his head and neck region (figure 1). There are brownish macules on the patient’s forehead, suggestive of café au lait spots (figure 2).

Figure 1.

A photograph depicting multiple skin-coloured nodular masses on the patients head and neck region.

Figure 2.

A photograph depicting brownish macules on the patient’s forehead, suggestive of café au lait spots.

There was no palpable lymphadenopathy. Intraoral examination revealed a solitary, well-defined 1.5×1 cm soft tissue mass on the hard palate, right of the midline, with normal overlying mucosa (figure 3). On palpation, the swelling was soft. An orthopantogram was taken to exclude a dental cause.

Figure 3.

An intraoral photograph demonstrating the soft tissue mass on the hard palate.

Investigations

Informed consent was gained and an incisional biopsy was completed under local anaesthetic to determine a histopathological diagnosis and exclude malignancy prior to treatment planning.

The histopathology report macroscopically detailed an ellipse of mucosal coloured tissue 11×3×4 mm. Microscopic examination demonstrated ‘within the polypoid piece of palatal mucosa (figure 4), there is an ill-defined dermal lesion composed of bland spindled cells within a loose fibrous stroma with scattered mast cells (figure 5) in keeping with a benign neurofibroma. There was no evidence of malignant features, such as cytological atypia, mitoses or necrosis.’

Figure 4.

Histopathology slide demonstrating the polypoid piece of palatal mucosa containing an ill-defined dermal lesion.

Figure 5.

Histopathology slide demonstrating bland spindled cells within a loose fibrous stroma with scattered mast cells.

A diagnosis of a neurofibroma of the hard palate was confirmed, based on clinical and histopathological findings.

Differential diagnosis

The differential diagnoses for this lesion included a fibroma, lipoma and neurofibroma. Based on the patients previously established diagnosis of NF1, the most likely diagnosis was neurofibroma or malignant neurofibroma. A diagnosis of a neurofibroma of the hard palate was confirmed, based on clinical and histopathological findings.

Outcome and follow-up

Following the histopathology report confirming no evidence of malignancy, the plan is for complete excision of the neurofibroma under a local anaesthetic.

Discussion

Neurofibromas can occur as isolated lesions or multiple, often being associated with NF, a genetic disease. NF is classified into three groups, NF1, NF2 and schwannomatosis.⁴

NF1 is the most prevalent and is a result of a mutation in the NF1 gene on chromosome 17. The NF1 gene is responsible for making the protein neurofibromin; this acts as a tumour suppressor. Mutations in the NF1 gene result in a non-functional neurofibromin that cannot regulate cell growth and division. Consequently, neurofibromas (peripheral nerve sheath tumours) form along nerves.²

NF1 is also known as von Recklinghausen’s disease. It affects men and women equally, all races and ethnic groups. It is autosomal dominant, around 50% of cases are inherited from a parent, and the rest of cases are caused by a spontaneous mutation.¹

The National Institutes of Health Consensus Conference, 1987, created a diagnostic criteria for diagnosis of NF1. A diagnosis can be confirmed if a patient has at least two of the symptoms mentioned in box 1.

Box 1. Diagnostic criteria for neurofibromatosis 1 (NF1)⁴.

• Six or more café-au-lait macules (>0.5 cm in children or >1.5 cm in adults).

• Two or more cutaneous/subcutaneous neurofibromas or one plexiform neurofibroma.

• Axillary or groin freckling.

• Optic pathway glioma.

• Two or more Lisch nodules (iris hamartomas).

• Bony dysplasia (sphenoid wing dysplasia, bowing of long bone±pseudoarthrosis).

• First-degree relative with NF1.

Additional signs and symptoms of NF1 that the patient has previously been diagnosed with are hypertension, renal artery stenosis and scoliosis. Other features may include short stature and macrocephaly.⁵

Oral neurofibromas most commonly involve the tongue, though have also been reported in other soft tissue sites. A lifetime risk of malignant transformation has been reported at 8%–13%, with 5% estimated to occur as neurofibrosarcomas with poor prognosis.⁶

Other oral manifestations of note include gingival enlargement and pigmentation, dental abnormalities of the mineralised structures, increased dental caries rate and osseous deformities.²

Learning points.

• Dental and oral care providers must be aware of the clinical oral manifestations of patients with neurofibromatosis (NF) as it can result in significant oral health compromise.

• NF can present within the oral cavity and has a risk of malignant transformation.

• A multidisciplinary approach with histopathology and maxillofacial teams is required to achieve a definitive diagnosis.