Solitary plexiform neurofibroma of the malar region: A rare and unusual presentation

Rajkumar K Prabhu; M Viswambaran

doi:10.4103/jodd.jodd_40_21

CASE REPORT

Year : 2022 | Volume : 16 | Issue : 1 | Page : 81-83

Solitary plexiform neurofibroma of the malar region: A rare and unusual presentation

Rajkumar K Prabhu, M Viswambaran
Air Force Institute of Dental Sciences, Agram Post, Bengaluru, Karnataka, India

Date of Submission	02-Oct-2021
Date of Decision	02-Oct-2021
Date of Acceptance	20-Dec-2021
Date of Web Publication	05-Apr-2022

Correspondence Address:
Rajkumar K Prabhu
Air Force Institute of Dental Sciences, Bengaluru - 560 007, Karnataka
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jodd.jodd_40_21

Abstract

Plexiform neurofibromas are benign tumors of the peripheral nerves and are usually considered pathognomonic of neurofibromatosis type 1. We discuss the case of a young male patient presenting with a solitary mass over the malar region. Pathologic examination revealed a plexiform neurofibroma of the infraorbital nerve. No other signs or symptoms of neurofibromatosis were identified. Although rare, plexiform neurofibromas may rarely occur as solitary lesions not associated with the neurofibromatosis spectrum. It can be seen in unusual anatomic location such as the malar region and should be considered in the diagnosis of soft tissue facial tumors.

Keywords: NF-1, Plexiform Neurofibroma, Facial region

How to cite this article:
Prabhu RK, Viswambaran M. Solitary plexiform neurofibroma of the malar region: A rare and unusual presentation. J Dent Def Sect. 2022;16:81-3

How to cite this URL:
Prabhu RK, Viswambaran M. Solitary plexiform neurofibroma of the malar region: A rare and unusual presentation. J Dent Def Sect. [serial online] 2022 [cited 2022 Aug 16];16:81-3. Available from: http://www.journaldds.org/text.asp?2022/16/1/81/342645

Introduction

Neurofibromatosis Type I (NF-1) is a disease that results from spontaneous mutations or familial transmitted mutations in the NF-1 gene located on chromosome 17q11.2. These mutations cause a loss-of-function in the protein neurofibromin, which typically functions as a tumor suppressor.^[1] The criterion for the diagnosis of NF-1 was established by the NIH in 1988 and is listed in [Table 1].^[2] According to some authors, the triad of multiple neurofibromas, cafe'-au-lait macules, and especially of Lisch nodules, is so reliable that their absence essentially excludes the diagnosis of NF-1.^[3],[4]

Table 1: NIH consensus guidelines: diagnostic criteria for neurofibromatosis^[2]

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Neurofibromas are benign peripheral nerve sheath tumors that present as focal cutaneous/subcutaneous or nodular/diffuse plexiform lesions. Although we typically associate the more visible cutaneous neurofibromas with NF-1 (around 99% incidence), plexiform neurofibromas are also seen in up to 50% of NF-1 patients.^[1] We present a case of a solitary plexiform neurofibroma of the malar region in a young male patient.

Case Report

A 22-year-old patient presented to us with a slowly growing, painless mass in the right malar region for the last 6 months. There was no history of other lesions or masses and no family history of similar lesions. General physical examination including the ophthalmologic and dermatologic examinations of the patient was normal. Facial movement and sensation were symmetric bilaterally. On inspection, the lesion appeared smooth, well circumscribed measuring approximately 2.5 cm × 2.5 cm without any secondary changes. It extended from a line drawn perpendicular to the lateral canthus, laterally over to the body of the zygoma. Palpation of the region revealed a firm, smooth nontender lesion freely movable over the underlying tissues extending from the left lateral brow medially over to the body of the zygoma.

Magnetic resonance imaging evaluation of the patient revealed a smooth homogeneous mass overlying the periosteum of the right malar region. The lesion appeared unencapsulated and hyperintense on T1 sections [Figure 1] and hypointense on T2 sections.

Figure 1: Axial T1 section showing a smooth homogeneous mass overlying the periosteum of the right malar region unencapsulated and hyperintense on T1 sections

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He was found to lack the typical signs of NF-1 with the absence of Lisch nodules, cafe'-au-lait spots, optic gliomas, multiple other neurofibromas or axillary/inguinal freckling. With clinical exclusion of NF-1, he was determined to have a solitary, nonsyndromic plexiform neurofibroma. The surveillance of the patient will include follow-up every 6 months for the 1^st year, then annually for 5 years.

Surgical procedure

The patient was taken for surgical excision of the lesion under general anesthesia. A minimal incision was designed within the relaxed skin tension lines of the malar region. Dissection extended through the subcutaneous tissues, the superficial musculoaponeurotic system layer to expose a flesh-colored, ovoid mass that appeared to have fibroadipose appendages. The mass was seen to have small finger-like extensions, which were traced until their termination. The mass was removed off the periosteum and noted inferiorly to be contiguous with the infra-orbital nerve [Figure 2].

Figure 2: The resected smooth lobulated mass with small finger-like extensions

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Histopathological examination

The gross tissue received a localized solitary lesion measuring 3 cm × 1.5 cm × 1.5 cm [Figure 3]. H and E sections of the lesion show a circumscribed lesion which is nonencapsulated with ill-defined margins. It consists predominantly of elongated spindle cells with poorly defined pale eosinophilic cytoplasm and tapering, wavy or brushed nuclei admixed with more indeterminate short spindle cells and numerous small nerve fibers set in a variably fibromyxoid matrix. The final pathological diagnosis was plexiform neurofibroma.

Figure 3: The lesion is composed of elongated spindle cells (H and E Stain ×4)

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Discussion

When evaluating soft-tissue lesions of the mid face, differential diagnosis can be quite broad, and includes hematoma, abscess, lipoma, arteriovenous malformation, pilomatrixoma, sebaceous cysts, and malignant entities. In the setting of a patient without obvious signs of NF-1, the diagnosis of a plexiform neurofibroma typically does not cross the mind of the clinician.

Plexiform neurofibromas originate from a proliferation of nerve sheath cells, extending across the length of the nerve, often involving multiple nerve fascicles, and ultimately creating a mass of thickened nerve branches.^[5] Under a microscope, these lesions are composed of a variety of elements including Schwann cells, collagen, fibroblasts, vascular cells and mast cell infiltrate as seen in [Figure 3]. Plexiform neurofibromas are a more aggressive subtype of neurofibroma, infiltrating through the soft tissue to grow along the length of the affected nerve. If the face is involved, significant disfigurement may be seen during the first 3 years of life.^[6]

These lesions can be seen throughout the body, including the head/neck region. The trigeminal nerve and its smaller branches are the most likely cranial nerves to be affected and involvement of the maxillary branch may cause proptosis or other disfiguring consequences as the tumor grows within the eyelid or orbit.^[5] Occasionally, plexiform neurofibromas may develop into malignant peripheral nerve sheath tumors, which confer a poor prognosis to the patient.^[1] Removal of the lesion is difficult due the significant infiltration of surrounding tissues and requires surgery for definitive treatment. Tumor recurrence is high and is two times more likely in cases presenting in the head/neck, two times more likely to recur if resected prior to 10 years old, and two times more likely to recur in a subtotal versus total resection.^[7] However, new modalities of treatment including Imatinib mesylate have shown promise in reducing tumor volume and activity, providing not only symptomatic, but therapeutic relief to the patient.^[6] Plexiform neurofibromas are described to be heavily linked to NF-1.

According to previous literature, their presence in an individual was described to be “pathognomonic” for NF-1.^[8] However, more recent papers suggest that this linkage may not be as strong as once thought; similar case reports have described isolated plexiform neurofibromas of the oropharynx, tongue, orbit, tip of nose, and palm in the absence of signs of NF-1.^{[9],[10],[11]} Our case was unusual in that it presented without family history or further systemic symptoms as described above. The location of the solitary plexiform neurofibroma in the malar region is a rare phenomenon, it should be considered in the differential diagnosis for an infra-orbital subcutaneous mass.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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