the 4 most important histological types of cancer in the small bowel are adenocarcinomas , neuroendocrine tumors , gastrointestinal stromal tumors , and lymphomas . small bowel adenocarcinoma ( sba ) represents approximately 40%percnt ; of small bowel cancers and carries a poor prognosis , with a 5-year overall survival ranging from 26 to 40%percnt ; [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ] . the duodenum is the most frequently involved segment , accounting for 5582%percnt ; of the cases , followed by the jejunum and the ileum . the prognosis of sba appears to be in between that of colon and gastric cancers , and complete surgical resection with locoregional lymphadenectomy remains the only potentially curative treatment . lymph node invasion is considered the main prognostic factor for localized sba [ 5 , 7 ] . in addition , the number of lymph nodes assessed and the number of positive lymph nodes seem to be of prognostic value . patients with stage iii sba and 3 invaded lymph nodes have a worse 5-year disease - free survival rate than patients with 1 or 2 invaded lymph nodes ( 37 vs. 57%percnt ; ) . however , even for patients with a high risk of recurrence after surgical resection , the role of adjuvant therapy remains largely unclear . human epidermal growth factor receptor 2 ( her2 ) overexpression or amplification has been reported in many epithelial malignancies . the role of her2-directed therapy and its success in breast cancer patients has led to the evaluation of protein overexpression , gene amplification , and antitumor activity of trastuzumab , an anti - her2 antibody , in multiple tumor types , including colorectal and gastric adenocarcinomas [ 9 , 10 ] . gene amplification and overexpression of her2 have been reported in approximately 15%percnt ; of gastric cancers . treatment with trastuzumab results in prolonged survival in gastroesophageal cancer if her2 is overexpressed or amplified in tumor cells . however , her2 status has not been well investigated in primary small intestinal adenocarcinoma , probably because of its rarity . unlike gastric adenocarcinomas , duodenal cancers seem to rarely harbor her2 amplification or overexpression [ 12 , 13 , 14 ] . we report the case of a patient with her2-positive stage iii duodenal adenocarcinoma who has received adjuvant chemotherapy , including trastuzumab . a 51-year - old , previously healthy man presented during routine follow - up with anemia ( hemoglobin 9.1 g / dl ) . an upper endoscopy was requested , which showed an ulcerated lesion in the third portion of the duodenum . staging computed tomography ( ct ) showed segmental wall thickening of the third duodenal portion , measuring 6 cm in length , without a clear cleavage plan with the pancreatic head . gastroduodenopancreatectomy was performed , and the pathology confirmed a pt2 pn1 ( 5 out of 19 lymph nodes positive ) , poorly differentiated adenocarcinoma of the duodenum ( fig . 2 ) . two months after the surgery , the patient was started on adjuvant chemotherapy with infusional 5-fluorouracil ( 5-fu ) 800 mg / m from day 1 to 5 and cisplatin 80 mg / m on day 1 every 3 weeks for 6 cycles . trastuzumab was administered as an intravenous infusion of 6 mg / kg ( initial loading dose of 8 mg / kg ) every 3 weeks during 6 cycles , followed by trastuzumab maintenance every 3 weeks until completing 1 year . during the first cycle , the patient developed grade 2 oral mucositis , and after the second cycle , a dose reduction of 5-fu to 650 on the fifth cycle of chemotherapy , the cisplatin dose had to be reduced to 60 mg / m due to progressive tinnitus . the patient successfully completed the planned 6 cycles of cisplatin , 5-fu , and trastuzumab and is currently receiving maintenance trastuzumab every 3 weeks for 1 year . studies conducted on the management of sba , such as adjuvant chemotherapy and radiation therapy , are limited by small sample sizes and series that are retrospective . clinical trials to determine optimal treatment regimens for patients with duodenal adenocarcinoma patients with those malignancies are frequently treated with either colorectal or gastric cancer drug regimens [ 15 , 16 ] . the absence of a well - established adjuvant treatment guideline for duodenal adenocarcinoma and the resultant poor patient survival underscore the importance of better understanding its biology in order to develop new therapeutic strategies . her2 is a transmembrane tyrosine kinase receptor , member of the her family ( her14 ) . her2 function and signaling activity requires receptor dimerization followed by transactivation of the tyrosine kinase portion of the dimer . phosphorylation leads to recruitment and activation of downstream proteins , and the signaling cascade is initiated . gene amplification induces protein overexpression in cell membranes and regulates signal transduction in cellular processes , such as proliferation , differentiation , and cell survival . aberrant her2 expression or function has been associated in carcinogenesis of breast , ovarian , gastric , prostate , salivary gland , and lung tumors . in her2-positive breast cancer , trastuzumab has shown a survival advantage in both early and metastatic scenarios and is currently the standard of care [ 18 , 19 , 20 ] . there is growing evidence that her2 is an important biomarker and key driver of tumorigenesis in gastric cancer , with studies showing amplification or overexpression in 734%percnt ; of tumors [ 11 , 21 ] . in preclinical models of gastric cancer , trastuzumab showed at least additive antitumor effects when combined with capecitabine or cisplatin , or both . in the pivotal phase iii toga trial , the addition of trastuzumab to cisplatin and 5-fu or capecitabine in patients with her2-positive tumors confirmed a better overall survival ( 13.5 vs. 11.1 months , p = 0.0048 ) when compared to chemotherapy alone . the prevalence of her2 overexpression and amplification in sba has only been investigated in few studies . in the one by overman et al . , only 1 out of 54 ( 1.7%percnt ; ) tumors expressed her2 on immunohistochemistry . similarly , in the study by aparicio et al . , her2 expression was observed in only 2 of 51 ( 3.9%percnt ; ) cases , both of them in the ileum , while no her2 expression was found in 32 patients with duodenal tumors . another study conducted immunohistochemical analysis and fluorescence in situ hybridization ( fish ) for her2 on 49 primary nonampullar small intestinal adenocarcinomas . the authors showed a complete lack of her2 protein expression in 47 cases ( 96%percnt ; ) by immunohistochemical analysis . only 2 cases ( 4%percnt ; ) showed a 1%plus ; staining pattern . on fish , none of the tumors , including those with 1%plus ; her2 immunoreactivity , exhibited her2 gene amplification . we describe the case of a patient whose resected stage iii duodenal adenocarcinoma stained positive ( 3%plus ; ) for her2 . based on the potential role of her2 as a driver of tumorigenesis and the beneficial effect of anti - her2 therapy in other malignancies , we discussed with the patient the potential advantages of combining trastuzumab to cisplatin and 5-fu for 6 cycles followed by trastuzumab maintenance for 1 year in the adjuvant setting in order to reduce the risk of recurrence . based on extrapolation from the toga trial results in the advanced scenario , the patient agreed to receive adjuvant anti - her2 therapy . adjuvant trastuzumab has proven benefits for patients with breast cancer and is still under study for gastroesophageal malignancies [ 23 , 24 ] . the question whether adjuvant anti - her2 therapy in combination with chemotherapy reduces the risk of duodenal adenocarcinoma recurrence will probably never be answered , given the rarity of those cases . the corresponding author acknowledges that she is responsible for complying with ethical requirements and declares that the patient was correctly informed and written informed consent was obtained ; the confidentiality of the patient was strictly preserved ; the patient was informed about the submission of the manuscript and will be acquainted when the article is published .
duodenal adenocarcinoma is a rare malignancy and carries a poor prognosis . 
 the role of adjuvant therapy and the optimal chemotherapy regimen remain largely unclear . treatment with trastuzumab results in prolonged survival in gastroesophageal cancer if human epidermal growth factor receptor 2 ( her2 ) is overexpressed or amplified in tumor cells . 
 however , unlike gastric adenocarcinomas , duodenal cancers seem to rarely harbor her2 amplification or overexpression . 
 we report the case of a patient with her2-positive stage iii duodenal adenocarcinoma who has received adjuvant chemotherapy including trastuzumab .