Immunohistochemical detection of SERPINB6, tryptase, and CD117 in mastocytosis. Tissue sections of 2 cutaneous mastocytomas in patient 12 (A-B, G) and patient 10 (C-D, H) and of systemic mastocytosis in patient 14 (E-F, I) were stained with mAb PI6-18 (A, C, E), antitryptase mAb AA1 (B, D, F), or anti-CD117 (G-I). Slides were stained with AEC (A-F) or DAB (G-I) and were counterstained with hematoxylin. Original magnification, × 400 (A-I).