[A CASE REPORT OF PRIMARY MUCOSA ASSOCIATED LYMPHOID TISSUE LYMPHOMA OF THE PROSTATE]

The patient was a 53-year-old man who was referred to the department of urology of our hospital after screening results indicated elevated prostate-specific antigen (PSA) levels. The PSA level was 5.33 ng/ml, and rectal examination revealed that the prostate was elastic and hard with mild prostatic hyperplasia. Because magnetic resonance imaging revealed abnormal signals in the prostatic transition area, prostate cancer was suspected and the patient underwent transrectal prostate needle biopsy. The pathological diagnosis was adenocarcinoma (Gleason score 5+5 = 10). After using thoracic, abdominal, and pelvic computed tomography (CT) and bone scintigraphy to confirm that metastasis had not occurred, robot-assisted radical prostatectomy (RARP) was performed. Prostate cancer was not detected during pathologic diagnosis of the surgical specimen, and on the basis of the results of re-examination with immunostaining, a diagnosis of mucosa-associated lymphoid tissue (MALT) lymphoma was made. In addition, an upper and lower endoscopy examination, positron emission tomography (PET) -CT, and bone marrow biopsy confirmed that generalized tumor lesions and lymph node swelling were not present, and the patient was diagnosed with primary MALT lymphoma of the prostate. Currently, 12 months since surgery, the patient continues to undergo follow-up as an outpatient and no recurrence has been observed. There have been only a few reports of primary MALT lymphoma of the prostate, in English or Japanese, and herein, we present our experience with a patient for whom a definitive diagnosis was difficult, along with a review of the literature.