The Normal and Neoplastic Perineurium

Abstract

Peripheral nerves consist of 3 layers with differing characteristics: the endoneurium, perineurium, and epineurium. The perineurium represents a continuum with the pia-arachnoid from the central nervous system and extends distally with the sheath of capsular cells of peripheral sensorial organs and propioceptive receptors. It is made of layers of flattened cells surrounded by a basement membrane and collagen fibers, forming concentrically laminated structures around single nerve fascicles. Functionally, the perineurium modulates external stretching forces (that could be potentially harmful for nerve fibers), and along with endoneurial vessels, forms the blood-nerve barrier. Multiple pathologic conditions associated with the perineurium have been described. Perineurial invasion is considered an important prognostic factor in several malignant neoplasms. Perineuriomas are true benign infrequent perineurial cell neoplasms that have been divided in 2 categories: those with intraneural localization and a more common extraneural (soft tissue) group, including sclerosing and reticular variants. Sporadic cases of malignant perineuromas have been reported. Interestingly, neurofibromas and malignant peripheral nerve sheath tumors may also display perineurial cell differentiation. The histologic appearance of perineuriomas may overlap with other soft tissue spindle cell neoplasms. Immunohistochemistry is imperative for the diagnosis, although in certain cases ultrastructural studies may be needed. Typical perineuriomas are positive for epithelial membrane antigen, glucose transporter-1-1, and claudin-1, and negative for S-100 protein and neurofilaments. Perineuriomas have mostly simple karyotypes, with one or few chromosomal rearrangements or numerical changes and it seems that specific cytogenetic aberrations may correlate with perineurioma subtype.

Intraoral Pseudo-Onion Bulb Intraneural Proliferations in a Patient with Hemimandibular Hyperplasia: A Case Report and Review of the Literature

“…Perineuriomas are benign neoplasms composed solely of perineurial cells [1]. There are two major types of perineuriomas: the more common extraneural or soft tissue type that is generally not associated with a major nerve and the intraneural type [1,2].…”

“…Immunohistochemically, perineuriomas are classically epithelial membrane antigen (EMA) positive and S-100 negative [1][2][3][4]. While EMA is very useful in the diagnosis of perineuriomas, it is not without drawbacks.…”

“…Histologically, intraneural perineuriomas show concentric cell layers of bland, spindle-shaped perineurial cells arranged in a pseudo-onion bulb pattern around the remaining nerve axon [1,2,4]. Immunohistochemically, perineuriomas are classically epithelial membrane antigen (EMA) positive and S-100 negative [1][2][3][4].…”

“…There are two major types of perineuriomas: the more common extraneural or soft tissue type that is generally not associated with a major nerve and the intraneural type [1,2]. The intraneural type is a rare neoplasm that most commonly arises in a nerve of the extremities in younger individuals [1][2][3][4].…”

Perineuroma of the skin negative for S100 protein but positive for stem cell antigens: A possible stem cell tumor

“…As mentioned above, the peripheral nervous system is composed of endoneurium, epineurium and perineirium. [1] Perineuroma and its related tumors of neurothekeoma and nerve sheath myxoma are categorized as per-ineural tumors, though the histological features were somewhat different from each other. [2][3][4][5][6][7][8] The classification and morphology of these three tumors are debatable; Table 1 shows brief characteristics of benign peripheral nerve tumors.…”