Background <p>Intravascular large B-cell lymphoma is a rare type of lymphoma. Although this tumor can occur in several parts of the body, primary intravascular large B-cell lymphoma of the prostate is extremely rare. Currently, there are only four case reports of primary large B-cell lymphoma in the prostate, and there is no comprehensive analysis of case series. Here, we report a case of intravascular large B-cell lymphoma originating from the prostate. Due to the unique morphology and atypical location of tumors under a microscope, pathologists often overlook them.</p> Case presentation <p>A 52-year-old Chinese male presented with frequent urination, urgency, and nocturia. Magnetic resonance imaging (MRI) showed prostate hyperplasia, while biopsy revealed the hyperplasia of prostate glands and stroma. A small area had dilated blood vessels, and there were many proliferating cells in the lumen. The cell nucleus was large, the nuclear cytoplasmic ratio was small, and the nuclear morphology was irregular. Multiple immunohistochemical staining were negative, but CD20 was positive. No other tumors were detected on the patient’s whole body scan. We diagnosed it as intravascular large B-cell lymphoma of the prostate.</p> Conclusion <p>In patients with benign prostate hyperplasia, proliferative blood vessels are found in the interstitium, and there is an accumulation of proliferative large cells in the lumen, which do not resemble endothelial cells, epithelial cells, tissue cells, or inflammatory cells. Pathologists should consider the possibility of intravascular large B-cell lymphoma and conduct immunohistochemical staining for large B-cell lymphoma. Primary intravascular large B-cell lymphoma of the prostate should be diagnosed after ruling out metastatic tumors.</p>