Neuroma

NEUROMA (neuroma), "tumor of nervous tissue", a collective designation for various growths, in one way or another connected with elements of the nervous system, but in their essence and structure being far from identical. Virchow divided all neuromas into false (tumor spurium) and true (tumor verum). To false N. he related tumors, although connected with nervous tissue, but consisting of some other tissue, for example connective, mucous, fatty; examples of false N., according to Virchow, are fibromas, myxomas, and lipomas developing from the perineurium of peripheral nerves and called neurofibromas, neuromyxomas (see), neurolipomas. To true N., according to Virchow, belong such tumors in which the tumor growth consists of elements of nervous tissue. These true N. Virchow subdivided into fibrous N., consisting only of nervous (myelinated and non-myelinated) fibers (tumor myelinicum and tumor amyelinicum), and cellular, ganglionic N. (tumor ganglionare), containing ganglionic nerve cells. In the further acceptance of the position that nervous fibers cannot be formed without nerve cells, the existence of true N. of fibrous type, i.e. consisting only of nervous fibers, became doubtful, and to true N. began to relate only such tumors which have in the basis growth of nerve cells both mature and immature. However, still somewhat later, after clarification of the possibility of formation of elements of nervous fibers from Schwann cells, as well as after observation of a number of cases of N. originating from cells of the type of indifferent neuroblasts capable of producing nervous fibers without formation of true ganglionic cells, it became clear that the existence of true neuromas consisting of nervous fibers and not containing ganglionic nerve cells is not paradoxical. In general Virchow's division of neuromas into false and true is retained and in the present time with the however reservation that the boundary between them is indistinct and that there exist forms of N. unclear, disputed. In particular in neurofibromas, neuromyxomas, neurolipomas, which were accepted to relate to false neuromas, growth of connective, mucous, and fatty tissue is sometimes combined with growth of elements of Schwannian sheaths of the type of neuroma (see), relating to true N.; even if this is not the case, then one can according to the opinion of some researchers think that in these tumors initially there was growth of the neuroma type (i.e. true N.), which in later times was replaced by growth of connective, mucous, or fatty tissue of the false N. type. To absolutely false N. relates amputation N., representing thickening of the end of the nerve cut off during amputation of a limb; this thickening has in the basis growth of connective tissue of the endo- and perineurium, accompanied by regenerative growth of nerve fibers coming from the cut nerve. To false N. of the amputation N. type belong growths of nerve fibers in various scars both operative and developing in the area of ulcer processes, for example in the bottom of a round ulcer of the stomach and duodenum, in the wall of the gallbladder in chronic cholecystitis, in the wall of the appendix after ulcerative appendicitis; some forms of N. of the appendix containing in themselves so-called argentaffin nerve cells are closer to ganglion-neuromas. To false N. belong still some of solitary forming on peripheral nerves nodes of neurofibromas (see), neurolipomas, as well as neuromas of Vater-Pacini bodies representing connective tissue growth of their sheath. True N. according to the proposal of Pick and Bielschowsky (Pick, Bielschowsky) are divided into 1) mature and 2) immature. 1. To mature relate those N. in which nervous elements have a fully mature or almost mature appearance. To these belong containing ganglionic nerve cells and nerve fibers ganglio-neuromas (see), observed in the central nervous system, up to the sympathetic system, in the adrenal glands, less often in other parts of the body. From N. of peripheral nerves to mature N. can be related solitary or multiple N. of the skin, mainly of limbs, emerging in the form of small painful nodules (tubercula, s. neuroma cutis dolorosa) and histologically consisting of a plexus of myelinated (tumor myelinicum) or non-myelinated (tumor amyelinicum) nerve fibers. The so-called tumor plexiforme, or Rankenneuroma, Rankenfibroma of the Germans, having the appearance of a ball of twisted and thick nerve trunks (see Neurofibroma), stands on the boundary between true and false N., since in it along with growth of connective tissue giving thickening of nerves there is also elongation of nerve fibers and besides new formation of nerve fibers [see separate table (pages 135-136), fig. 3]. 2) Immature N. have in the basis growth of immature nerve cells-neurocytes, neuroblasts, sympathogoni,-which gives formation of a cell mass similar to round-cell sarcoma or to some types of glioma (formation of rosettes); by the method of silvering in such tumors sometimes one can discover newly formed nerve fibers. Some of immature N. flow as malignant tumors, destroying neighboring tissue and giving metastases. These tumors arise most often in the sympathetic nervous system, in paraganglia, and in the medullary substance of the adrenal glands from embryonal, undifferentiated sympathetic nerve cells, sympathogoni; therefore the most common name for them at present is sympathogonioma; they are also called neurocytomas, neuroblastomas, neurosarcomas, etc. (see Ganglion-neuroma). In some of the tumors relating to these, cells are more differentiated and reveal the presence in the protoplasm of chromaffin substance, which gives occasion to call them chromaffinomas, pheochromocytomas, paragangliomas. To immature N., developing from peripheral nerves, relate neuromas (see). Most N. represent new formations developing on the ground of defective development of various parts of the nervous system; in particular immature neuromas are probably formed from preserved from embryonic life undifferentiated nervous elements of the neuroblast type capable of development of ganglionic cells, nerve fibers, and neuroglia; in connection with this such tumors sometimes approach gliomas. Some of N. are difficult to consider true tumors-blastomas; for example mature ganglion-neuromas and some N. of peripheral nerves sometimes stand closer to defects of development of the hamartoma type (see) and choristoma, than to tumors. Treatment. Amputation N. is removed by operative means. In order to prevent recurrence the cross-section of the nerve after removal of N. is recommended to be smeared with strong carbolic acid (Fedorov) or 5% formalin (Foerster). Applied for this purpose neurotomy above the nerve or crushing of the nerve (neurotripsia) are less effective.