A case report of primary prostate intravascular large B-cell lymphoma

RATIONALE: Primary intravascular large B-cell lymphoma (IVLBCL) is a rare and aggressive extranodal lymphoma that rarely affects the prostate. Its nonspecific clinical and laboratory features often lead to misdiagnosis as benign prostatic hyperplasia (BPH) or prostatitis, delaying appropriate treatment. We report a case of primary prostatic IVLBCL initially misdiagnosed as BPH, highlighting the diagnostic challenges and the importance of comprehensive pathological evaluation. PATIENT CONCERNS: A 75-year-old male presented with a 1-year history of a weakened urinary stream, dribbling, increased nocturia, and urinary urgency. Symptoms transiently improved with self-medication of the α1-blocker tamsulosin but later recurred. DIAGNOSES: Histopathological examination revealed clusters of atypical tumor cells within the prostatic vasculature. Immunohistochemistry showed positivity for leukocyte common antigen, Vimentin, CD20, and CD79a, with a Ki-67 index > 90%. A final diagnosis of primary intravascular large B-cell lymphoma of the prostate was established. INTERVENTIONS: Following diagnosis, the patient and his family declined any antitumor therapy (including chemotherapy) and opted for best supportive care and were discharged against medical advice. OUTCOMES: The patient died 5 months after diagnosis without receiving any subsequent antitumor therapy. LESSONS: Prostatic IVLBCL is a diagnostic mimic of BPH and requires a high index of suspicion. Immunohistochemistry and molecular studies are essential for accurate diagnosis. Early recognition and appropriate chemotherapy can improve outcomes in this rare malignancy.