Neurilemmoma (Schwannoma) of the Facial Nerve Presenting as a Parotid Mass

Abstract

Eighty percent of all asymptomatic parotid masses are benign neoplasms. Pleomorphic adenoma, Warthin's tumor, oncocytoma, monomorphic adenoma, and the benign lymphoepitheliallesion are the most common tumors. Sebaceous adenoma, sebaceous lymphadenoma, and the papillary ductal adenoma are encountered infrequently. A facial nerve neurilemmoma manifesting as a parotid mass is a rare occurrence. CASE REPORTA 39-year-old man manifested a 6-month history of a painless mass in the region of the right parotid that he stated fluctuated in size throughout the day. There was no history of facial weakness and the physical examination revealed a 1 x 2 em firm mass in the tail of the parotid gland. Facial nerve function was normal. A computed tomography scan, performed at the referring institution, confirmed a 2 cm mass in the tail of the parotid gland (Fig. 1). Fine-needle aspiration biopsy was not performed.A superficial parotidectomy with facial nerve dissection was planned. After the skin flaps were raised and the usual landmarks were identified, it was apparent that the mass was deep to the main trunk of the facial nerve. On closer examination, fascicles of the facial nerve could be seen splayed out over the lateral surface ofthe mass. Proximally the lesion extended into the temporal bone, and distally 1 em of normal facial nerve trunk was seen. A mastoidectomy revealed fusiform swelling of the facial nerve from the distal vertical segment to the stylomastoid foramen (Fig. 2). The lesion was resected with the facial nerve and the frozen section revealed a neurilemmoma. The margins were clear and a graft using the greater auricular nerve was placed in the fallopian canal. 8-0 nylon suture was used for the distal anastomosis. The next day a gold weight From the Departments of Otolaryngology (Drs. Prasad, Myers, and Kamerer) and Pathology (Dr.

Fine Needle Aspiration Biopsy of Intraparotid Schwannoma

“…Their nuclei are usually hyperchromatic and have tapered ends, unlike the rounded ends of Schwann cell nuclei. 2,4,8 Immunohistochemically, neurofibroma may be S-100 protein positive but less strikingly so as compared with schwannoma.…”

“…The correct preoperative diagnosis should lead to a conservative surgical procedure (enucleation) with nerve preservation, the treatment of choice for this lesion. 2,12 Since many of these lesions are uncommon, more experience is needed, and schwannoma should be kept in mind when dealing with parotid and other head and neck fine needle aspirates showing a significant spindle-shaped cell component. …”

“…Of these, pleomorphic adenoma and Warthin's tumor are the most common and are relatively easily diagnosed by fine needle aspiration. 1 Facial nerve schwannomas, in contrast, also known as neurilemmomas, that sometimes present as parotid masses, are among the most rare clinical occurrences and should not be confused with other spindle cell lesions, especially neurofibroma, 2 with which they share a common precursor, the Schwann cell, as well as cytologic features. These neoplasms are usually solitary, benign, slowly growing, encapsulated tumors that arise from the sheath of peripheral and cranial nerves.…”

Giant malignant peripheral nerve sheath tumor of the neck in a patient with neurofibromatosis-1

“…The risk of malignant transformation is about 3-14% [4,6,7,8], which is highly expected in NF-1 rather than NF-2, with a latency period of about 10-20 years [2]. Malignant transformation is more common in deeply situated giant neurofibromas rather than superficial ones.…”

Diagnosis and management of intraparotid facial nerve schwannoma

“…The most diagnostic feature of intraparotid FNS is intraoperatively difficulty locating the facial nerve (Avery and Sprinkle, 1972;Hehar et al, 1999). In addition, tumours intimately involved with, or difficulty dissecting the facial nerve during superficial parotidectomy have been reported (Prasad et al, 1993). Frozen section of the lesion can help to make the diagnosis.…”