Neurinoma

NEURINOMA, neurinoma (from Greek neuron-nerve and inos-fiber), a fibrous tumor of nerve origin. The term N. was proposed in 1908 by Verocay to designate distinctive tumors that develop most often on peripheral nerves, less frequently on cranial nerves, in the form of multiple soft nodules of various sizes. Characteristic of these tumors is that they consist of spindle-shaped cells and delicate fibrillar substance, and the latter, based on its reaction to stains (van Gieson, Mallory), is found not to belong to connective tissue, but represents a special immature tissue of neurogenic origin. Neither neurofibrils nor glia does this fibrillar substance give reactions. The spindle-shaped nuclei with the mentioned fibrillar substance may be arranged in bundles interwoven in different directions; but especially typical for N. are the pictures when the spindle-shaped nuclei are arranged closely next to one another in the form of a fence, forming parallel wavy rows; between each pair of opposing rows of nuclei lies an anuclear fibrillar substance consisting of short parallel-running fibrils, as if stretched between the opposing rows of cells. These distinctive figures, designated as 'bands of transversely arranged nuclei', as 'palisade', 'rank' arrangement of nuclei, as 'barrel figures', are sometimes also found in other tumors and, according to the research of Lauche, represent an expression of rhythmic multiplication of tumor nuclei [see separate table (pp. 607-608), figure 7]. As the research of Verocay and several other authors has shown, N. develops from cells of the Schwann sheaths of nerves, and the source of its development is probably not mature Schwann cells, but embryonic neurocytes preserved in the nerve sheaths. On this basis, N. can be called neurocytomas and classified as immature neurromas (see), resp. ganglioneuromas (see). Regarding the nature of the fibrillar substance in N., views differ. Verocay and several authors consider it immature nervous tissue; others believe it belongs to neuroglia. On the basis that in some N. ganglion nerve cells and nerve fibers were found, and in others the formation of true neuroglia ('neurinogliomas') was proven, one can think of the ability of the parent cells of the tumor to differentiate in the directions of both nervous and glial tissue. Sometimes in N. there is proliferation of connective tissue ('fibro-neurinomas').--Verocay put forward his doctrine of N. in relation to the multiple systemic affection of nerves, designated as 'Recklinghausen's disease' or neurofibromatosis (see), and expressed the thought that all neurofibromas are based on neurinomas. It was later found that N. can be observed not only in the form of multiple affection of nerves, but also as solitary tumors, sometimes arising from large nerves, and sometimes from small nerve branches; some N. probably develop on the basis of embryonic mixing of neurocytes. In particular, N. and neurinogliomas develop in the form of separate, often symmetrical nodules in the auditory nerves, in the cerebellopontine angles, in the membranes of the brain and spinal cord, in the roots of the latter, under the skin, in the vermiform appendix, in the walls of the stomach and intestines, in the uterus, etc. It should be borne in mind, however, that rhythmic multiplication of nuclei and the formation of parallel bands from a fence of transversely arranged nuclei are also found in other tumors, for example in fibromas, fibrosarcomas, especially in leiomyomas; rarely in normal smooth muscle tissue as a result of its spasmodic contractions, a similar arrangement of nuclei can be found. Therefore, to diagnose N. only on the basis of the above-mentioned figures of nuclear arrangement is impossible; for this, the entire histological picture of the tissue must be taken into account, often with the condition of applying special staining methods (van Gieson, Mallory).-The course of typical N. is benign; however, some of them may exhibit malignant course, similar to sarcoma. Microscopically in such neurinomas, polymorphism of nuclei and loss of regular structure are found. Such tumors are called neurinoma sarcomatodes' (syn. neurosarcoma).

A.

Abricosov.