Schwannoma and Neurofibroma, Originating from the Ulnar Nerve in Neurofibromatosis: A Case Report and Review of the Literature

Abstract

Schwannomas and neurofibromas are rare benign tumors originating from the peripheral nerve sheath. Tumors in neurofibromatosis are mostly neurofibromas and often appear in the soft tissue of peripheral nerves. In this report, a patient presented with two large adjacent soft tissue tumors in the right wrist and distal forearm which originated from a common nerve. A schwannoma had formed beside a neurofibroma from the ulnar nerve and induced numbness and paresthesia in the little and ring fingers. Although the patient had café au lait spots on the skin, neurofibromatosis was not suspected due to lack of symptoms. The patient was referred to the current research clinic suffering from two soft tissue masses in the wrist and ulnar nerve dysfunction. In neurofibromatosis patients, two tumors of a different nature originating from a common nerve close together have rarely been described in the literature. The patient was treated by en bloc excision of the mass while protecting the nerve fascicles. The follow-up results indicated no neurological symptoms and complete restoration of ulnar nerve function.

Atypically Located Solitary Neurofibroma of the Ulnar Nerve as Inaugural Presentation of a New Genetic Variant of Neurofibromatosis Type 1: A Case Report

“…1 , 3 , 5 , 6 The incidence rates of NFs located in the hand are 0.8% in the general population and between 10% and 15% within patients with NF-1. 4 The presence of a solitary NF of the ulnar nerve at the level of the hand is extremely uncommon; also, to our knowledge a solitary NF of the ulnar nerve with an extrafascicular location, outside of Guyon canal, has not been previously described in the literature. Also, to our knowledge there are no reports regarding a symptomatic, solitary NF of the ulnar nerve as an inaugural presentation of NF-1.…”

“…Neurofibromas can be classified regarding to their location, morphology, and growth pattern as either solitary (also known as localized, sporadic, or nodular form), diffuse cutaneous (more common at the head and neck), plexiform (multinodular tumors associated with deep nerves or plexus), or massive soft-tissue form (often a diffuse infiltration of a distal extremity). 2 , 3 , 4 , 6 , 7 The solitary NF is the most commonly found subtype (approximately 90%), and usually emerges from superficial cutaneous nerves as extraneural and pediculated in relation to the nerve. More rarely, a solitary NF may originate from deep-located nerves, and will typically result in fusiform expansion of the nerve trunk (intraneural subtype).…”

“…Solitary NFs may have a variable initial presentation, ranging from an asymptomatic, slow-growing tumor that is incidentally found to neurogenic dysfunction with progressive pain, weakness, hypoesthesia, and tingling due to the mass’ effect upon adjacent nerves. 3 , 4 , 6 Neurologic symptoms are more likely when the NF originates from a deep-seated nerve, whereas superficial NFs are usually small, asymptomatic masses. 6 …”

“…Despite NF being described in the literature as a benign tumor, there is a 3% to 15% reported risk of malignant transformation. 4 , 5 In fact, only the plexiform, massive-sized, and localized intraneural forms of NF have been found to be important precursors of malignant PNSTs (MPNSTs). 2 , 4 Although only a small proportion of patients with NF-1 (about 5%) develop MPNST, up to 50% to 60% of MPNSTs occur in patients with NF-1.…”

“…Neurofibromas (NFs) are uncommon, benign peripheral nerve sheath tumors (PNSTs) that result from the abnormal proliferation of Schwann cells and fibroblasts. 1 , 2 , 3 , 4 , 5 Almost 90% of the NFs occur sporadically, whilst 10% are associated with neurofibromatosis type-1 (NF-1). 1 , 3 , 5 , 6 The incidence rates of NFs located in the hand are 0.8% in the general population and between 10% and 15% within patients with NF-1.…”