Pictorial Essay: Imaging of Peripheral Nerve Sheath Tumours

Abstract

Peripheral nerve sheath tumours (PNST) may be benign or malignant. Benign PNSTs include neurofibroma and schwannoma. Neurogenic tumours share certain characteristic imaging features, suggested by a fusiform-shaped mass with tapered ends, the "split-fat" sign, atrophy of the muscles supplied by the involved nerve, the "fascicular sign," and the "target sign"; these imaging features are best demonstrated on magnetic resonance imaging. This pictorial essay emphasizes the characteristic signs and distinguishing features of PNSTs on imaging.

Neurofibroma of Base Tongue in a Young Boy

“…Target sign may be present. Neurofibroma and Schwannoma appear similar in MRI, except nerve can be identified in Schwannoma and more often shows degenerative changes [2]. Treatment of choice for peripheral nerve sheath tumour is surgical excision.…”

“…Localised neurofibroma generally is slow growing, mostly arising from cutaneous nerve and rarely from deep nerves [2]. Plexiform neurofibroma generally detected early in life.…”

“…Up to 10% of these lesions are associated with Neurofibromatosis, an autosomal dominant disorder. Neurofibroma can be of three subtypes-localised, diffuse and plexiform [2,3]. Plexiform neurofibroma is least common and is pathognomic of von Recklinghausen disease, seen in 17 -30 % of patient, caused by mutation of NF1 gene in chromosome 17.…”

“…The most common sites in Head and Neck are temple, back of the neck and tongue. Oral manifestation are described in only 4-7% of patient, and tongue is the most common site [2,4,5]. Approximately 5-10% of Plexiform neurofibroma undergo malignant transformation and their rate of growth is inversely proportional to age.…”

Schwannoma of the Lower Leg with Malignant Transformation. A Case Report

“…Benign peripheral nerve tumours are seen as fusiform-shaped soft-tissue masses with low-to-intermediate signal intensity on T1-weighted images and high signal intensity on T2-weighted images that are contiguous with the nerve of origin, and show muscular fatty atrophy, complete split-fat sign and target sign. Larger (>5 cm), heterogeneous masses with central necrosis and ill-defined margins are more likely to be malignant [11] . The ultrasonographic features of benign and MPNST are variable and differentiation between schwannomas, neurofibromas and MPNST is very difficult.…”