Cutaneous Intraneural Perineurioma: A Case Report

Clinical Features, Natural History, and Outcomes of Intraneural Perineuriomas: A Systematic Review of the Literature

BACKGROUND

Intraneural perineurioma is a rare peripheral nerve sheath tumor characterized by localized proliferation of perineurial cells. The literature consists predominantly of case reports and institutional series, with inconsistent and confusing nomenclature. We present a pooled analysis of all reported cases of intraneural perineurioma in the literature.

METHODS

A systematic search of PubMed, MEDLINE, Embase, and Scopus was performed according to PRISMA guidelines to identify all reported cases of intraneural perineurioma in the literature. Individual cases were pooled and analyzed for demographics, clinical features, and outcomes.

RESULTS

A total of 172 cases were identified across 72 studies, of which 149 were found in major peripheral nerves and their branches. Median age of patients at diagnosis and onset of symptoms was 18 years (interquartile range [IQR], 12-34 years) years and 13.5 years (IQR, 8-26 years), respectively, with 54.4% (81/149) being female. The most common sites were the sciatic nerve or its branches (41.9%), median nerve (13.5%), radial nerve (12.2%), and brachial plexus (12.2%). Most patients were managed conservatively (52.9%; 72/136). Among those managed conservatively with available follow-up (n = 31), median follow-up was 11 months, and most (67.7%, n = 21) reported no change in neurologic status, although worsening was noted in 29.0% (9/31). Among surgically managed cases (n = 64), the most common intervention was resection with or without repair (62.5%; 40/64), neurolysis (25%; 16/64), or tendon transfers without resection (12.5%; 8/64). No lesion recurred after surgical resection.

CONCLUSIONS

Intraneural perineurioma represents a benign focal lesion presenting with weakness and atrophy affecting adolescents and young adults. Most cases are managed nonoperatively and surgical treatment strategies are varied.

On pseudo-onion bulb intraneural proliferations of the non-major nerves of the oral mucosa

Perineurial cells (PCs) participate in reactive and neoplastic processes, of the latter pure perineurial being intraneural (IP) and soft tissue perineuriomas with oral examples being reported in both. In our review of over 500 peripheral nerve sheath tumors including granular cell tumor, we identified a single ostensible case of IP occurring on the tongue of a 45-year-old African-American male that was characterized by classic perineurial pseudo-onion bulbs (PsOb), proliferating PCs among these PsOb, sclerosis apparently due to long term duration and a plexiform pattern. We have also encountered 37 examples of apparently reactive, hyperplastic or traumatic, PsOb intraneural pseudoperineuriomatous proliferation (IPP) simulating microscopically some of the properties of IP. The majority of the lesions occurred in women and close to 80 % affected the tongue. Three microscopic patterns were appreciated. Type I lesions were those where IPP was seen only focally, type II where it was seen in roughly half of the lesion, and type III where the majority of the lesional tissue or the lesion itself was characterized by IPP. Immunohistochemically, IPP featured PsOb with generally a single layer of PCs decorated by epithelial membrane antigen, glut-1 or claudin-1, and decreased numbers of S-100 positive Schwann cells. The number of axons was not apparently altered. A prominent collagenous intraneural component was occasionally evident among PsOb and the affected nerve featured discontinuous or absent perineurial envelop. While type I and II IPP can be distinguished from IP, the distinction from type III lesions can be problematic. However, the discontinuity of the perineurium of the affected nerve, the spacing and collagenization among PsOb, the limited perineurial cell layer defining the pseudo-onion bulbs, the absence of proliferating PCs between PsObs and the decreasing number of Schwann cells may be of help in the distinction from IP.