[Primary malignant lymphoma of the prostate: report of a case achieving complete response to combination chemotherapy and review of 22 Japanese cases].

A 70-year-old man presented with complaints of difficult urination, perineal pain and lassitude. An enlarged, hard and nodular prostate was palpable on digital rectal examination. Needle biopsy of the prostate was performed, which revealed diffuse large B-cell non-Hodgkin's lymphoma by immunohistochemical studies. Right internal and external iliac nodes were swollen on computed tomographic scan (CT) of the pelvis. No abnormal finding was seen on abdominal CT, upper gastrointestinal fiberscopy and bone marrow histology. Therefore, the disease was classified into the clinical stage II according to Ann Arbor's criteria. The patient achieved complete response (CR) to five cycles of combination chemotherapy, CHOP, and survives more than two years without recurrence. Primary malignant lymphoma of the prostate is a rare prostatic malignancy. Only 22 Japanese cases with primary prostatic lymphoma have been reported to our knowledge. In 23 cases including ours the majority of the patients were older than 60 years, and their histopathology was mostly diffuse lymphoma, which belongs to intermediate grade of non-Hodjkin's lymphoma according to the Working Formulation's Classification. Nineteen out of 23 cases (83%) were divided into localized stage i.e. stage I or II. In these reports, three of five cases treated with either radical prostatectomy or radiotherapy alone resulted in death or progressive disease. On the other hand, 11 out of 16 cases (69%) who received chemotherapy alone or with other therapy obtained CR. Primary lymphoma of prostate has previously been considered to have a poor prognosis. Our results, however, suggest that patients with this malignancy respond well to combined chemotherapy, and could possibly be cured when the disease is confined to the localized stage.