Fibrovascular Tumor-Like Lesions of the Facial Nerve

Abstract

Background: Facial nerve tumors (FNTs) are relatively rare benign lesions that arise from any segment of the facial nerve (FN). About half of all patients present with FN dysfunction, mainly long-standing or progressive facial paralysis. Diagnosis of an FNT is usually based on radiological imaging and confirmed by histological study. Most reported cases of FNTs are schwannomas and hemangiomas.

Objectives: The aim of this study was to review 4 cases of lesions with clinical, radiological, and surgical findings that suggested an FNT, the pathology revealing a fibrovascular proliferation with no clear signs of a specific tumor.

Method: Medical records of patients who had surgery due to an FN lesion were reviewed. Cases with known tumoral lesions were excluded. Four patients with tumor-like lesions were identified. Their imaging studies were re-evaluated. The pathological study included hematoxylin-eosin, Masson's trichrome, and immunohistochemistry for S100 protein, neurofilaments, CD31, Wilms' tumor 1 (WT1), and D240.

Results: The 4 cases revealed tumor-like fibrovascular lesions that could not be classified as typical pathological entities. All cases had a complete facial palsy preoperatively. Computed tomography and magnetic resonance imaging (MRI) suggested schwannoma or hemangioma. A complete excision was achieved, and a facial reconstruction was performed immediately after interruption. Postoperative FN function was improved in all cases. The histological study showed nervous tracts of normal morphology, with fibrous and vascular tissue interspersed in variable proportions. All cases showed areas of fibrosis with Masson's stain. In all cases, nervous tissue and Schwann cells tested positively for neurofilaments and S100, respectively. In vascular areas, endothelial cells stained positively for CD31, and negatively for D240 and WT1.

Conclusions: Fibrovascular lesions of the FN may mimic primary FNTs, especially schwannomas and hemangiomas. Surgical excision with grafting or nerve transfer is the procedure of choice if a complete facial paralysis is found. This unusual condition should be considered when counseling patients with FN lesions. The lack of hyperintensity on MRI T2-weighted images may suggest the presence of fibrous tissue.

Keywords: Facial nerve tumors; Facial paralysis; Fibrovascular lesion; Tumor-like lesions.