in the united states , prostate cancer constitutes approximately 21% of new cases of cancer among men and is the cause of 14% of all cancer death in men . prostate adenocarcinoma still represents about 90% of prostate cancer cases   with few incidences of lymphoma of the prostate , the majority of which are of diffuse large b - cell non - hodgkin subtype . non - hodgkin lymphoma ( nhl ) of the prostate is classified into primary or secondary based on whether the cancer is localized to the prostate gland . primary nhl of the prostate is characterized by the presence of an enlarged prostate at the beginning of the disease , localization of the tumor to the prostate gland , and the absence of involvement of any other tissue or lymphoid node within 1 month of diagnosis [ 3 , 4 ] . a 54-year - old male with a past medical history of benign prostatic hyperplasia presented with complaints of worsening urinary urgency and weak urinary stream . he was unable to void despite medical therapy , and transurethral prostatic resection ( turp ) utilizing a coagulating intermittent cutting device was recommended . physical examination was normal , and digital rectal exam showed a firm and enlarged prostate without nodular surface . an initial laboratory test showed hemoglobin of 14.5 g / dl ( normal 13.517.5 ) , wbc of 8.4  10/l ( normal 3.510.5 ) , platelet count of 378  10/l ( normal 150450 ) , and serum prostate - specific antigen of 2.03 ng / ml ( normal 04 ) . turp showed an enlarged prostate with a total volume of approximately 67.2 ml , with hypoechoic regions consistent with benign prostatic hyperplasia . a computerized tomography scan of the neck , chest , abdomen , and pelvis revealed diffuse urinary bladder wall thickening and an enlarged prostate , as well as a 2.4-cm soft tissue mass within the cecum involving the ileocecal valve , and no evidence of obstruction ( fig . . following colonoscopy , the increased metabolic activity noted in the cecum was determined to correlate with a large tubulovillous adenoma with high - grade dysplasia and 2 smaller tubular adenomas , but no colitis or diverticulitis . tissue obtained during turp was sent for pathologic evaluation and immunohistochemical analysis and revealed prostatic tissue essentially replaced by large atypical neoplastic lymphoid cells within a background of small reactive t lymphocytes . the large atypical cells were pleomorphic with irregular nuclear contours and occasional cleaved nuclei , and prominent nucleoli were also identified ( fig . 3b ) , and bcl-2 ( variable positivity ) , while lacking expression of cd5 , cd10 , ae1/3 , ema , p501s , and pap . the overall morphology and immunohistochemistry profile was noted to be diagnostic of diffuse large b - cell lymphoma ( dlbcl ) ( fig . bone marrow aspiration was performed that showed polytypic b cells comprising approximately 1% of total cells and t cells without immunophenotypic aberrancy . a bone marrow core biopsy showed normocellular marrow with adequate multilineage hematopoiesis , no evidence of lymphoma or metastatic malignancy , and adequate iron storage . cytogenetic examination of 20 metaphase cells revealed a normal male diploid karyotype with no consistent numerical or structural chromosome aberrations . the patient was treated with r - chop followed by radiation without any obvious complications . 2b , c ) showed complete remission , and the patient has been disease free for the past 2 years with continuing surveillance in our clinic . nhl involving the prostate accounts for 0.09% of prostate cancers and 0.1% of all nhl [ 5 , 6 ] . various subtypes of nhl of the prostate have been reported , including but not limited to follicular lymphomas , burkitt lymphomas , mantle cell lymphomas , and mucosa - associated lymphoid tissue lymphomas ; however , dlbcl remains the most common [ 4 , 5 , 6 , 7 ] . the majority of reported prostate nhl are secondary in origin , representing late manifestation of advanced nodal disease . based on the literature , primary extranodal lymphoma of the prostate is extremely rare , representing about 0.20.8% of extranodal lymphomas [ 9 , 10 ] , and it usually occurs in the 6th decade of life . to the best of our knowledge , our case is the only reported case of primary dlbcl of the prostate , localized only to the prostate without nodal involvement or distant metastasis . both primary prostate lymphoma and other prostate - related conditions , such as benign prostatic hyperplasia , have similar clinical features ; therefore , misdiagnosis of dlbcl is common . however , confirmation of the diagnosis can be made by flow cytometry and immunohistochemical analysis of prostatic tissue . imaging modalities such as computed tomography and magnetic resonance imaging scans are often nonspecific for diagnosing dlbcl of the prostate . pet is helpful in determining the metabolic f - fluorodeoxyglucose activity in suspicious lesions and is useful in disease monitoring prior to and after treatments . currently , there is no consensus on therapeutic modalities for treatment of primary dlbcl of the prostate . preceding the development of adequate chemotherapy and radiotherapy for lymphoma , a retrospective study by bostwick et al while some current studies have shown excellent outcomes with anthracycline - based chemo- and radiotherapy , others have shown equally good outcomes with r - chop with or without radiotherapy . the r - chop regimen has shown better disease - free survival in primary dlbcl compared to disease with nodal involvement or extensive disease , after correction for the differences in the international prognostic index score . the impressive efficacy seen with r - chop has been attributed to the synergistic effect of rituximab with chop , which enhances the chemo - sensitivity of the lymphoma cells . rituximab ( rituxin , biogen / genentech , san francisco , ca , usa ) is a monoclonal antibody against cd20 , a highly expressed cell surface protein in dlbcl . our patient was treated with an r - chop regimen followed by 36 gy of fractionated radiotherapy to the prostate and entire seminal vesicles ( 18 fractions of 2 gy ) . primary prostate lymphoma developed metastasis within 159 months following diagnosis , thus necessitating the need for closer surveillance during this period . although the prognostic outlook for primary dlbcl of the prostate is determined by histological type and stage of the disease , curative response to chemotherapy has been well documented . primary extranodal lymphomas of the prostate , although a rare entity , can occur in men in their 6th decade of life . including primary prostate lymphoma in the differential diagnosis of patients with obstructive urinary symptoms is imperative due to similar clinical features to other prostate - related conditions , such as benign prostatic hyperplasia . despite the lack of consensus on the choice of treatment modality , based on currently available data posttreatment surveillance , especially within the first 5 years when disease relapse is most common , and enrollment in a clinical trial when available is highly recommended . this research did not receive any specific grant from funding agencies in the public , commercial , or not - for - profit sectors .
we report a case of primary diffuse large b - cell lymphoma of the prostate in a 54-year - old caucasian male who presented with urinary retention and benign prostatic hyperplasia . 
 we discuss the rare presentation of this disease and its clinicopathologic features and review the literature for up - to - date information on the diagnosis and clinical management . despite the low incidence of lymphoma involving the prostate gland , 
 it should always be considered as part of the differential diagnosis in cases of prostate gland enlargement with urinary tract obstructive symptoms resistant to medical therapy . 
 treatment modalities for this rare disease are also discussed .