The article presents a clinical case of mantle cell lymphoma of the prostate in a 75-year-old man who was hospitalized in the Emergency Urological Department of the City Clinical Hospital No. 52 with gross hematuria through cystostomy tube. During examination the patient was found to have prostatomegaly (prostate volume 992 cm3), prostate-specific antigen level was 2.2 ng/mL. Immunohistochemical examination of prostate tissue after adenectomy indicates prostate damage due to mantle cell lymphoma.