Primary Prostatic Diffuse Large B‐Cell Lymphoma Mimicking Prostate Cancer With a Normal Prostate‐Specific Antigen Level

Introduction Primary prostatic lymphoma is rare and may mimic prostate cancer clinically and radiologically. Case Presentation A 66‐year‐old man was referred for evaluation of suspected advanced prostate cancer. Despite a normal prostate‐specific antigen level of 0.573 ng/mL, imaging revealed a prostatic mass with suspected bladder invasion and bilateral hydronephrosis. Prostate needle biopsy showed atypical lymphocytic infiltration but could not distinguish lymphoma from inflammatory changes. Additional transurethral biopsy provided sufficient tissue for histopathological and immunohistochemical evaluation, establishing a diagnosis of primary prostatic diffuse large B‐cell lymphoma. Conclusion Primary prostatic lymphoma should be considered when clinical and imaging findings suggest prostate cancer despite a normal prostate‐specific antigen level. Additional tissue sampling should be considered when needle biopsy is inconclusive despite persistent clinical suspicion of lymphoma.