[' The aim of this study was to investigate the association of the expression of tumor necrosis factor-α (TNF-α) with asymptomatic inflammatory prostatitis National Institutes of Health (NIH) category IV and prostatic calculi, in patients with obstructive benign prostatic hyperplasia (BPH) treated by transurethral electroresection of the prostate (TURP).', " Ninety-six patients with obstructive BPH and TURP were evaluated in a prospective study. Based on a preoperative transrectal ultrasound examination of the prostate gland, patients were divided into two groups, one with prostatic calculi (n = 31) and one without (n = 65). Prostatitis NIH category IV was classified according to Irani's histological grading system (Irani et al. J Urol 1997;157:1301-3). Associations between the incidence of prostatic calculi, histological prostatitis, TNF-α expression, prostate-specific antigen, uric acid, cholesterol, triglycerides, C-reactive protein, International Prostate Symptom Score (IPSS), the International Index for Erectile Function (IIEF-5) and the NIH-Chronic Prostatitis Symptom Index Score (NIH-CPSI) were analyzed.", ' Prostatitis was confirmed by histological investigation in 71.9% of patients: 83.9% of those with prostatic calculi versus 66.1% of those without (p < 0.04). TNF-α expression was significantly higher in patients with prostatic calculi. Association calculations yielded significant values for the severity (histological grading) of inflammation (p < 0.029), TNF-α expression (p < 0.007), uric acid (p < 0.005), cholesterol (p < 0.028) and the NIH-CPS subdomain of urinary symptoms (p < 0.044) in patients with prostatic calculi.'] Is tumor necrosis factor-α expression in patients with obstructive benign prostatic hyperplasia associated with a higher incidence of asymptomatic inflammatory prostatitis NIH category IV and prostatic calcification?