Microscopic findings of serous borderline tumor. (a and b) Hematoxylin and eosin stain, (a) magnification, ×20; bar, 500 μm; (b) magnification, ×200; bar, 50 μm. Detection with (c) 5B2 (magnification, ×200; bar, 50 μm) and (d) 22A31 (magnification, ×200; bar, 50 μm) anti-mesothelin monoclonal antibodies.