IHC analysis of CTSB expression in lung SCC and adjacent normal tissues. (A) Staining against CTSB showed significant differences between lung SCC and adjacent normal tissues, and overexpression of CTSB was likely to present with bad differentiation. IHC (a: adjacent normal tissues; b: well differentiated, weakly positive; c: moderately differentiated, moderately positive; d: poorly differentiated, strongly positive.); H & E (e: adjacent normal tissues; f: well differentiated; g: moderately differentiated; h: poorly differentiated). (B) Kaplan-Meier curves and statistics showed the correlation between CTSB expression and decreased survival. The 5-year survival rates were 41%, 20% and 2% for weak, moderate and strong staining samples, respectively, when CTSB was assessed as a marker (Statistical difference: weak VS moderate: P = 0.041; weak VS strong: P = 0.009; moderate VS strong: P = 0.021). Multivariate analyses using Cox proportional hazard model also showed that CTSB could also be developed as a prognostic factor for lung SCC. (C) Patient data showed the 2-year metastatic rates were 9%, 21% and 44% for weak, moderate and strong staining samples; the 5-year metastatic rates were 27%, 41% and 71% for weak, moderate and strong staining samples, respectively, when CTSB was assessed as a marker. Therefore, CTSB expression might affect metastatic capacity of lung SCC.