[Schwannoma of the nose and paranasal sinuses].

A rare case of a Schwannoma (neurinoma) of the frontal sinus of a 75-year old male patient was examined clinically, histologically, and by electron microscopy. The fine structure of neurinomas occurs in two forms: Type Antoni A is composed of Schwann cells whose nuclei are arranged in palisading rows with greatly attenuated cytoplasmic processes extending from the Schwann cells in parallel alignment; Antoni B is characterized by loosely arranged Schwann cells set in meshwork of macrocysts and reticular fibers. It may be a degenerative form of Antoni A. In the present case Antoni A was the dominating pattern. A prominent basal lamina enveloping Schwann cells, as well as desmosome-like junctions between them, were identified. Furthermore, myelin figures, lysosomal bodies, intranuclear unmyelinated axons and concentric laminated inclusions, and annulate lamellae were found in Schwann cells. Luse bodies appeared in the tumour matrix. It is suggested that annulate lamellae may play a significant role in cell differentiation and tumour growth. No other ultrastructural signs of malignancy were seen.