Fine needle aspiration of schwannomas. Value of electron microscopy and immunocytochemistry in the preoperative diagnosis.

In the absence of Verocay bodies, the cytologic appearance of schwannomas can be quite nonspecific, with the differential diagnosis including a number of spindle cell lesions. The diagnostic accuracy can be enhanced by the use of electron microscopy (EM) and immunocytochemistry; both techniques are easily applicable to aspirated material. Six cases of schwannoma, diagnosed as such preoperatively by the application of these techniques, are reported. Only two of the cases showed Verocay bodies on light microscopy. Electron microscopy, performed on four cases, revealed a complex arrangement of long cell processes, with scattered desmosomelike structures, a prominent focally reduplicated basal lamina and long-spacing collagen. All of the cases showed positive staining for S-100 protein.