The term Neuroma is applied to almost all forms of tumours in the course of nerves, and as the majority of these do not consist of nervous tissue, they are to be regarded as false neuromata. In the true neuroma there is new-formation of nerve fibres which form a considerable portion of the tissue (see Fig. 84, p. 227). The false neuromata are mostly fibrous tumours of nerves, and there are two forms which deserve special mention.
Plexiform neuroma consists of a series of thickened cords composed of connective tissue in the midst of which the nerve fibres are contained.
The connective tissue may, to a considerable extent, take the characters of mucous tissue.
Multiple neuromata are really fibrous-tissue tumours, and as such are described at p. 212.
Sarcoma is very rare in nerves. Cancers do not occur as primary tumours, but nerves are often involved in the extension of such tumours from neighbouring parts. It often happens that a cancer or sarcoma grows around a nerve, which passes through its midst without becoming the seat of the tumour tissue. This is again to be associated with the apparent independence of the lymph spaces in nerves. Sometimes, however, a cancer breaks into a nerve, and grows in the lymph spaces between the perineurium and the bundle of fibres. In such cases the nerve fibres undergo degeneration.
Ranvier, Lemons sur l'histologie du systeme nerveux, 1878; Cornil et Ranvier, Histol. path., 2nd ed., 1881, i., 661; Wolberg, Deutsch. Zeitschr. f. Chir., xviii. and xix., 1883 (with literature); Pitres et Vaillard, Arch. d. phys., v., 1885; Stroebe, (Degeneration and Begeneration) Ziegler's Beitrage, xiii., 1893; Weir Mitchell, Injuries of Nerves, 1872; Weir Mitchell, Morehouse, and Keen, Gunshot wounds and other injuries of nerves, 1881; Leyden, (Ascending neuritis) Volkmann's Vortrage, Syd. Soc. transl., 1876; Bowlby, Injuries and Diseases of Nerves, 1889; Kennedy, (Degeneration and Begeneration) Phil, trans, of Boy. Soc, vol. clxxxviii., p. 257, 1897, and (historical with literature) Proceed. Phil. Soc. of Glasgow, 1897-98. Multiple neuritis - see full account by Buzzard, Harveian Lectures, in Lancet, 1885, vol. ii., also separate publication; Drummond, Peripheral paralysis, 1888; Finlay, Trans. Med. Chir. Soc, 1887; Boss, Med. Chronicle, 1890; Boss and Bury, On Peripheral neuritis, 1893. Tumour - see literature under Neuroma, p. 228.