Increased number of mast cells in PCL. (A) Skin biopsies from patients with PCL (All; n = 43) subdivided into patients with CTCL (n = 35) and CBCL (n = 8), from subjects with normal skin (Ctrl; n = 12) and from patients with inflammatory cutaneous diseases (All; n = 24), such as psoriasis (n = 8), atopic dermatitis (AD; n = 8) and pseudolymphoma (Pseudolym; n = 8) were stained by immunohistochemistry with anti-tryptase antibody. The number of tryptase-positive mast cells was analyzed by microscopic counting of 5 high power fields at 200× magnification and calculating the mean number of mast cells per mm². Data represent the mean ± SEM. Statistical significance was assessed by 2-tailed Student t test. (B) The number of tryptase-positive mast cells was counted separately in the center (filled columns) and in the periphery (striped columns) of PCLs. Data represent the mean ± SEM. Statistical significance was assessed by 2-tailed Student t test. (C) Normal skin, magnification 200×. (D) Psoriasis, magnification 150×. (E) Atopic dermatitis, magnification 150×. (F) Pseudolymphoma, magnification 150×. (G) CTCL, plaque stage, magnification 200×. (H) CTCL, tumor stage, magnification 50×, staining of mast cells with anti-tryptase antibody (brown).