Numbers of mast cells correlate with progression of PCL. (A) The number of tryptase-positive mast cells was analyzed by microscopic counting of 5 high power fields at 200× magnification in skin biopsies from CTCL patients with MF, FMF, and SS grouped according to ISCL/EORTC classification (IA, n = 13; IB, n = 8; IIA, n = 1; IIB, n = 4; IIIB, n = 2; IVA, n = 1), into patients with stable (n = 21) and progressive (n = 8) disease, into patients with MF (n = 23), FMF, (n = 3) and SS (n = 3), into patients with different clinical stages (Eczema, n = 13; Plaque, n = 10; Tumor, n = 3; SS, n = 3), or into patients with different MF stages (Eczema, n = 13; Plaque, n = 8; Tumor, n = 2). Data represent the mean ± SEM. Statistical significance was assessed by 2-tailed Student t test. (B) Progression-free survival, defined as duration (years, months) from initial diagnosis until first change of treatment because of disease progression, was determined for each group of patients. Data represent the mean ± SEM. Statistical significance was assessed by 2-tailed Student t test. (C) Kaplan-Meier curves were generated for CTCL patients with MF, FMF, and SS grouped according to the ISCL/EORTC classification, into stable and progressive disease, and into < 100 mast cells/mm² and > 100 mast cells/mm². In addition, patients with MF and FMF were grouped into those with < 100 mast cells/mm² and > 100 mast cells/mm². Statistical significance was assessed by Log-rank test. One patient with stage IIA showed an exceptionally long progression-free survival of more than 30 years (purple line).