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follicular lymphoma is the most common subtype of non - hodgkin s lymphoma ( nhl ) 1 
 2 .
gastrointestinal follicular lymphoma mainly comprises scattered small whitish nodules , mass lesions and polyps , while other signs are exceedingly rare .
the recent development of enteroscopy devices , such as double - balloon enteroscopy ( dbe ) and capsule endoscopy , allows gastroenterologists to detect atypical lesions of gastrointestinal follicular lymphoma .
herein , we report an unusual case of gastrointestinal follicular lymphoma presenting with an annular ulcer .
she had no history of abdominal surgery or use of non - steroidal anti - inflammatory drugs ( nsaids ) .
laboratory findings included hemoglobin 5.9  g / dl and mean corpuscular volume of 63.0  fl .
enhanced computed tomography ( ct ) of the abdomen revealed swelling of multiple intraperitoneal lymph nodes and a high density of mesenteric adipose tissue ( fig .  1 ) .
fluorodeoxyglucose ( fdg)-positron emission tomography ( pet ) showed high fdg accumulation at the intraperitoneal lymph nodes .
dbe was performed using a retrograde approach , and severe stenosis with an annular ulcer was detected in the lower ileum ( fig .  2 ) . 

enhanced computed tomography ( ct ) of the abdomen revealed swelling of multiple intraperitoneal lymph nodes ( arrow ) and a high density of mesenteric adipose tissue . 

double - balloon enteroscopy ( dbe ) was performed using the anal approach , and severe stenosis with an annular ulcer was detected in the lower ileum .
the differential diagnosis of ileal annular ulcers includes intestinal tuberculosis , nsaid - related ulcers , crohn s disease , localized ischemia of the small intestine , and lymphoma .
nsaid - related ulcers were ruled out because she had no history of taking nsaids .
histologic examination of biopsy specimens from the ileal ulcer revealed a concentration of medium - sized atypical lymphocyte - like cells that were immunohistochemically positive for cd10 , cd20 , and bcl-2 antibodies , and negative for cd3 and cd5 antibodies ( fig . 
fluorescence in situ hybridization analysis showed igh - bcl2 rearrangement in 67  % of the ileal ulcer cells ( fig . 
she was diagnosed with primary ileal follicular lymphoma , stage ii2 based on the lugano classification due to metastasis to distant abdominal lymph nodes . 

histologic examination of biopsy specimen from the ileal ulcer ( photomicrograph original magnification    400 ) , and fluorescence in situ hybridization ( fish ) analysis .
chemotherapy with rituximab and bendamustine was selected because of her advanced age and the low grade malignancy of follicular lymphoma .
combination chemotherapy with rituximab and bendamustine has equivalent effects and lower toxicity than polypharmacy with rituximab , cyclophosphamide , hydroxydaunorubicin , oncovin , and prednisone ( r - chop ) in nhl with low grade malignancy such as follicular lymphoma .
moreover , swelling of multiple intraperitoneal lymph nodes observed with enhanced ct , and high fdg accumulation at the intraperitoneal lymph nodes with fdg - pet also disappeared .
most cases of follicular lymphoma are initially detected in the lymph nodes , and widespread nodal involvement such as ann arbor stage iii or iv is a typical presentation of this disease , whereas only 5    10  % of patients present with early stage i or ii 3 . the gastrointestinal tract is the common site of extra - nodal nhl 1 
 2 .
although extra - nodal involvement usually occurs as a result of disseminated nodal disease , primary gastrointestinal nhl accounts for 30    40  % of all extra - nodal nhl 4 .
most common subtypes of primary gastrointestinal nhl are mucosal - associated lymphoid tissue lymphoma or high grade diffuse large b - cell lymphoma , while primary gastrointestinal follicular lymphoma is a relatively rare disease accounting for only 1  % of gastrointestinal nhl 5 .
gastrointestinal follicular lymphoma lesions comprise mainly scattered small whitish nodules 1    2  mm in diameter and subsequent mass lesions with or without ulceration .
in previous studies of 222 cases with small intestinal follicular lymphoma , scattered small whitish nodules , mass lesions , and polyps were detected as follicular lymphoma lesions in the small intestine in 183 cases ( 82.4  % ) , 29 cases ( 13.1  % ) , and six cases ( 2.7  % ) , respectively , and other morphology was detected in only four cases ( 1.8  % ) 1 .
studies performed before the introduction of dbe or capsule endoscopy revealed that gastrointestinal follicular lymphoma lesions were mostly unifocal , and the proportion of ileal localization was low 6 
 7 
 8 .
recent studies , however , reported that dbe detected new jejunoileal follicular lymphoma lesions in 73    85.7  % of cases with duodenal follicular lymphoma 6 
 7 .
moreover , 24 of 33 patients with gastrointestinal follicular lymphoma ( 72.7  % ) who underwent enteroscopy had multifocal involvement , mostly in the duodenum and ileum 1 .
in addition , fdg - pet was not always effective in detecting gastrointestinal follicular lymphoma lesions , because three - quarters of patients with gastrointestinal follicular lymphoma who had been diagnosed by dbe were negative for fdg - pet 8 .
therefore , investigation of the small intestine is recommended for the diagnosis of gastrointestinal follicular lymphoma . with the increasing use of dbe for observation of small intestinal lesions , the frequency of gastrointestinal follicular lymphoma with atypical changes might increase .
based on the present case , gastrointestinal follicular lymphoma should be considered in the differential diagnosis of annular ulcers in the small intestine .
a 72-year - old woman presented with symptomatic anemia without abdominal symptoms . 
 she had no history of abdominal surgery or use of non - steroidal anti - inflammatory drugs . 
 enhanced computed tomography of the abdomen revealed swelling of multiple intraperitoneal lymph nodes and a high density of mesenteric adipose tissue . 
 fluorodeoxyglucose ( fdg- ) positron emission tomography showed high fdg accumulation at the intraperitoneal lymph nodes . 
 double - balloon enteroscopy detected severe stenosis with an annular ulcer in the lower ileum . 
 she was diagnosed with ileal follicular lymphoma based on histologic examination and fluorescence in situ hybridization analysis of the biopsy specimen . 
 the ileal ulcer was successfully treated by chemotherapy with rituximab and bendamustine for 1 year . 
 we strongly recommend consideration of gastrointestinal follicular lymphoma in the differential diagnosis of annular ulcers in the small intestine .