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Background: The most common malignancy to cause gastric outlet obstruction is primary gastric adenocarcinoma and it is followed by carcinoma of the pancreas and gallbladder. Herein, we report a case of gastric outlet obstruction secondary to metastatic lobular breast carcinoma.Case Presentation: Fifty-seven year old Caucasian female with recently diagnosed metastatic lobular breast carcinoma to skin was referred to gastroenterology for evaluation of dyspepsia and dysphagia. She has past medical history significant for acid reflux and Clostridium difficile colitis. Computed tomography of her abdomen showed diffused bowel wall thickening without evidence of bowel obstruction. Due to persistent abdominal pain, an upper endoscopy was performed. The upper endoscopy showed gastritis and gastric stenosis in the gastric antrum. These lesions were biopsied and dilated with a balloon dilator. The biopsy of the gastric antrum later showed a metastatic carcinoma of breast origin with typical tumor morphology and immune-phenotype.Conclusions: Differentiating metastatic breast carcinoma from primary gastric adenocarcinoma cannot be done using histological examination alone. Immunohistochemistry is needed to differentiate the two based on staining for estrogen and progesterone receptors. The presence of gross cystic disease fluid protein 15 is also suggestive of metastatic breast carcinoma. The stomach has a significant capacity to distend (up to 2-4 L of food) and malignant gastric outlet obstruction is often undetected clinically until a high-grade obstruction develops. Our case demonstrates valuable teaching point in terms of broadening our differentials for gastric outlet obstruction. When patients present with gastric outlet obstruction, both non-malignant and malignant causes of gastric outlet obstruction should be considered. Once adenocarcinoma has been determined to be the cause of gastric outlet obstruction, further immunohistochemistry is needed to differentiate breast carcinoma from other carcinomas. [ABSTRACT FROM AUTHOR]

Expression of gastrointestinal biomarkers MUC1, MUC2, MUC5AC, small-intestinal mucin antigen (SIMA), villin, and CDX2 has been studied in colorectal adenocarcinoma (CRC). Little is known, however, about their expression in small-intestinal adenocarcinoma (SIA). We immunohistochemically compared 30 SIAs with 48 CRCs for the expression of these biomarkers. The results showed that all 6 proteins were variably expressed in SIA, but the frequencies of expression were significantly lower than those for CRC with the exception of MUC1. Specifically, positive staining for MUC1, MUC2, MUC5AC, SIMA, villin, and CDX2 was observed in 16 (53%), 17 (57%), 12 (40%), 15 (50%), 20 (67%), and 18 (60%) of SIAs and 25 (52%), 43 (90%), 39 (81%), 45 (94%), 47 (98%), and 47 (98%) of CRCs, respectively. In addition, SIAs more frequently exhibited a focal staining pattern for MUC2, MUC5AC, SIMA, and villin, whereas more diffuse immunoreactivity was evident in CRCs. Focal staining for MUC1 and diffuse staining for CDX2 were common for SIAs and CRCs. Furthermore, poorly differentiated SIAs tended to express MUC1 more frequently when compared with well- and moderately differentiated SIAs. These observations further support the notion that SIA is immunophenotypically distinct from CRC despite their morphologic similarity. [ABSTRACT FROM AUTHOR]