Oral Lipomatous Neurofibroma: A report of two cases and a review of the literature

Abstract

Neurofibroma is a benign tumor that originates from the peripheral nerve sheath. This lesion may assume multiple growth patterns and various histologic variants have been described in the literature. We present two cases of lipomatous neurofibroma, a rare variant in the oral cavity. This variant is typically seen as a cutaneous lesion predominately located in the head and neck. Case 1 was a 62-year-old female who presented with a mass of her left posterior palate. Case 2 presented as a submucosal dorsal tongue mass in an 18-year-old male. Both lesions appeared clinically benign. Neither patient had a known history of neurofibromatosis type 1. The biopsies from case 1 and case 2 showed similar histopathological features. These two lesions were well delineated submucosal tumors characterized by an admixture of spindled neural cells and mature adipocytes. The mature adipocytes were separate from the regional adipose tissue. The spindle cells contained serpentine nuclei set in a wavy well-vascularized fibrillar stroma. The immunohistochemical staining for both lesions revealed S100 positivity of the tumor cells and negative staining for CD99, CD34, and BCL2. Differential diagnosis for these tumors included solitary fibrous tumor and spindle cell lipoma. However, based on the lack of a hemangiopericytoma-like vascular pattern, wire-like collagen and the pattern of IHC staining, these entities were excluded. While the diagnosis of a conventional neurofibroma is straightforward, the diagnosis of a lipomatous neurofibroma may be more challenging. Neither of our patients had a known history of Neurofibromatosis type 1 (NF1); however, cutaneous lipomatous neurofibromas have been associated with NF1. Therefore, a patient with a diagnosis of lipomatous neurofibroma should have a medical work-up to exclude this syndrome. With the presentation of two cases of lipomatous neurofibroma arising intraorally, we hope to raise awareness of this distinct and rare morphologic subtype of neurofibroma.