Antoni type B areas of 11 neurinomas were examined with an electron microscope. The ultrastructure of this tissue form proved that the type B neurinoma results from degenerative changes of type A tissue. The degenerative character of type B cells is indicated (i) by cytoplasmic organelles and (ii) by changes of the cyto-structure which are caused by the loss of lamellar systems, giving the individual cell a more rounded profile. Consequently, (iii) the intercellular space becomes wider and its content modified. Single cells may lie isolated within a wide intercellular space, which may be filled with an amorphous mass. Under the light microscope this arrangement appears as a reticular formation. - A comparison between the results of studies with light and electron microscopes revealed that what is usually called hyaline" is in fact an intercellularly deposited amorphous material derived from basement membranes. The reticulin-like fibres observed after silver impregnation are usually basement membranes enveloping the tumour cells and their processes. © 1969 Springer-Verlag."
