human immunodeficiency virus ( hiv ) infection can cause defects in cell - mediated immunity , and these defects increase the incidence of various malignancies . acquired immune deficiency syndrome ( aids)-defining malignancies include kaposi 's sarcoma , non - hodgkin 's lymphoma , primary central nervous system lymphoma , and invasive cervical cancer . highly active antiretroviral therapy ( haart ) has led to a dramatic decrease in aids - related mortality as well as the incidence of opportunistic infections and aids - defining malignancies . however , many cancers not previously identified as aids - defining malignancies are now emerging as important causes of death in persons living with hiv [ 4 , 5 , 6 ] . such non - aids - defining malignancies include anal , liver , skin , and other cancers . an increased prevalence of oncogenic viral coinfection can explain the higher incidence of particular cancers such as liver , cervical , and anal cancer , as well as non - hodgkin 's lymphoma . in south korea , there are no clear patterns in the relative increase of non - aids - defining malignancies and the reduction of aids - defining malignancies after haart [ 7 , 8 ] . non - hodgkin 's lymphoma is most frequently observed in aids - defining malignancies , and gastrointestinal malignancies are common among non - aids - defining malignancies . although men who have sex with men ( msm ) are at highest risk for hiv acquisition in south korea , the anal cancers associated with hpv infection are rarely reported . the concurrence of non - hodgkin 's lymphoma and squamous cell carcinoma in the rectum in hiv - infected msm has not been reported yet . we report a case of rectal squamous cell carcinoma that occurred with metachronous diffuse large b cell lymphoma in an hiv - infected msm . a 51-year - old homosexual male with 10-year history of hiv infection presented to the emergency department with complaints of repeated bloody stool ( three instances ) . he had received haart , but his haart treatment regimen had to be altered several times due to adverse events , poor adherence and virologic failure . he was taking lamivudine , stavudine , lopinavir - ritonavir and abacavir at the time of admission . he denied any symptoms , including fevers , chills , night sweats or weight loss , except hematochezia . on physical examination , the abdomen was soft and there were no palpable masses or tenderness . his cd4 + t cell count was 116/mm , and his hiv viral load was 2,730 copies / ml . epstein barr virus ( ebv ) polymerase chain reaction ( pcr ) showed 27,750 copies / ml . sigmoidoscopy demonstrated a 75% circumferential ulceroinfiltrative lesion in the rectum and a biopsy was performed ( fig . pathologic diagnosis was diffuse large b - cell lymphoma with cd20 ( + ) , cd3 ( - ) , cytokeratin ( - ) , and ki-67 ( 90% ) ( fig . the staging work - up including a bone marrow study revealed lymphoma of the anorectum , nasopharynx , upper neck lymph node , and bone marrow with ann arbor stage iv in july 2007 . chemotherapy was initiated with a regimen of rituximab combined with etoposide , vincristine , doxorubicin , cyclophosphamide , and prednisone for 4 cycles , and vincristine , doxorubicin , cyclophosphamide , and for 2 cycles . positron emission tomography - computed tomography performed in december 2011 showed higher fluorodeoxyglucose uptake in the rectum . in january 2012 , a sigmoidoscopy and biopsy were performed and the pathologic diagnosis was high - grade squamous epithelial dysplasia ( fig . at that time , the patient 's hiv viral load titer was 80 copies / ml , and his cd4 + t cell count was 312/mm with a regimen of lamivudine - abacavir , darunavir , ritonavir and etravirine . well - differentiated squamous cell carcinoma could not be ruled out and the clinical stage was t2n1m0 , iiia . concurrent chemoradiation therapy was initiated with 5-fluorouracil and mitomycin c. after treatment , there was no evidence of disease . in february 2013 , well - differentiated squamous cell carcinoma was diagnosed with sigmoidoscopic biopsy and the patient was treated with laparoscopic - assisted abdominoperineal resection ( fig . 2c ) ; the pathologic stage was determined to be t2n0m0 , i. the patient continued to visit the outpatient department after discharge without significant complaint or sign of recurrence . in the past , opportunistic infection was the main cause of death in hiv - infected patients ; however , with the advent of haart , hiv - infected patients are surviving for much longer and instead are facing chronic diseases such as cardiovascular disease , liver disease , and cancer . haart has led to a great decrease in the incidence of opportunistic infections and aids - defining malignancies . in the haart era , we can assume a decrease in the proportion of aids - defining malignancies , but an increase in non - aids - defining malignancies [ 9 , 10 ] . in south korea , there has been no evidence of change in the incidence of aids - defining malignancies or non - aids - defining malignancies [ 7 , 8 ] . seol et al . investigated the prevalence of malignancies in hiv - infected patients , and reported similar incidence of aids - defining and non - aids - defining malignancies during the pre - haart and haart period , respectively . reported approximately the same prevalence with cancer occurring in 33 patients ( 3.75% ) out of 850 patients . choe et al . did not draw any conclusion about whether the incidence of aids - defining malignancies decreased after haart , however , because of the small size of the study population . two studies from south korea showed only 3 rectal adenocarcinoma cases among 59 hiv - infected patients with malignancies [ 7 , 8 ] . one anal squamous cell carcinoma was reported but rectal squamous cell carcinoma was not reported . the majority of colorectal malignancies both in the general population and among hiv - infected patients are adenocarcinomas . however , higher proportions of other cancer histologies were identified unlike those seen in the general population . compared to the general population , more hiv - infected patients were diagnosed with squamous cell carcinoma ( 2.5% vs. 0.04% , respectively ) , small cell carcinoma ( 1.6% vs. 0.08% , respectively ) , and leiomyosarcoma ( 0.9% vs. 0.04% , respectively ) . hiv infection increases susceptibility to virally promoted cancers such as burkitt 's lymphoma and hodgkin 's lymphoma ( ebv infection ) , kaposi 's sarcoma ( human herpesvirus-8 [ hhv-8 ] infection ) , and anogenital carcinoma ( hpv infection ) . several hpv types have been known as the oncogenic agents responsible for the cervical squamous carcinomas . molecular mechanisms for hpv - associated carcinogenesis have been described , mediated by hpv e6 and e7 oncoproteins . recent studies reported that the most common hpv type detected in anal squamous cell carcinoma is hpv 16 , but non hpv 16 subtypes were also detected [ 11 , 14 , 15 ] . unfortunately , in this case , pcr test for hpv was not performed . in the present case , the cd4 + t cell count was 116/mm at dlbcl diagnosis and 312/mm at squamous cell carcinoma diagnosis , respectively . a cd4 + t cell count below 200/mm was reported to have a meaningful relationship with the occurrence of malignancy in choe 's study . there was an increase in the proportion of patients with cd4 + t cell counts above 200/mm , which emphasizes the risk of malignancy , even in the context of immune reconstitution . it is clear that the importance of early diagnosis and prevention of cancer in hiv - infected patients should be emphasized . non - aids - defining malignancy such as hpv - associated anorectal cancer is an emerging problem for hiv - infected persons in south korea . the screening and prevention of cancers should be included in the clinical care of hiv - infected individuals .
diffuse large b cell lymphoma ( dlbcl ) is one of the most common acquired immune deficiency syndrome ( aids)-defining malignancies among human immunodeficiency virus - infected patients , and rectal cancer has recently emerged as a prevalent non - aids - defining malignancy . 
 we report a case of rectal squamous cell carcinoma that was metachronous with dlbcl in an hiv - infected patient who was receiving highly active antiretroviral therapy . 
 the patient was diagnosed with dlbcl and showed complete remission after chemotherapy . 
 follow - up imaging showed increased uptake at the rectum , previously treated as lymphoma . 
 repeated biopsy was performed and squamous cell carcinoma of the rectum was reported . 
 after concurrent chemoradiation therapy , curative resection was performed .