Schwannomas


Microscopic features: Schwannomas are usually solitary, well circumscribed, encapsulated lesions, mostly confined to the subcutis. Multinodular lesions may be present in the dermis, this is known as 'plexiform neurilemmoma'.
The characteristic features include presence of alternating Antoni A and Antoni B areas
Antoni A area is composed of spindle shaped Schwann cells arranged in interlacing fascicles.There may be nuclear palisading. In between two compact rows of well aligned nuclei , the cell processes form eosinophilic Verocay bodies. Mitotic figures may be present (usually less than 5 per 10 high power field).
Antoni B area consists of loose meshwork of gelatinous and microcystic tissue. Large, irregularly spaced, thick walled blood vessels are noted in Antoni B area. These may contain thrombus material in the lumina.