Image Description
Deep-seated schwannomas (mediastinum or retroperitoneum) of long standing may show several degenerative changes. One of the frequent findings in such cases is the presence of ectatic, tortuous blood vessels with thickened hyalinized walls (as shown here). The surrounding stroma contains small clusters of schwann cells with degenerative-type atypia and a few inflammatory cells.
About the Disease
Schwannoma is a slow-growing, encapsulated benign peripheral nerve sheath tumor that is usually seen sporadically (90% of cases). The remainder are associated with Neurofibromatosis 2 (3%), schwannomatosis (2%), or multiple meningiomas with or without NF2 (5%). Schwannomas may rarely arise in the setting of NF1. The most common locations are head, neck, upper and lower extremities, posterior mediastinum, and retroperitoneum. The cut surface is yellow-white or gray. Secondary changes such as hemorrhage, cystic change, cytologic atypia, and calcification are more frequent in the larger deep-seated tumors. Schwannomas are composed of cellular Antoni A areas alternating with hypocellular Antoni B areas. Schwann cells in Antoni A areas show nuclear palisading, whorling patterns, and Verocay bodies. Antoni B areas consist of spindle cells in a loose myxoid or hyalinized stroma, inflammatory cells, collagen fibers, and ectatic deformed vessels with hyalinized walls and thrombi. Schwann cells consistently show positivity for S-100 and SOX10. Cellular schwannoma is composed of mainly Antoni A areas and shows increased mitotic activity (usually < 4 mitoses/10 HPF). They are usually found in deep-seated locations and behave in a benign fashion. Plexiform schwannomas are superficial and multinodular and make up about 5% of all schwannomas. The linkage to Neurofibromatosis 1 or 2 is weak, unlike the strong association between plexiform neurofibroma and NF1. References: 1) Enzinger & Weiss's Soft Tissue Tumors, Sixth Edition, 2014; p. 813-829.