SATB2 in Neoplasms of Lung, Pancreatobiliary, and Gastrointestinal Origins.

<bold>Objectives: </bold>Special AT-rich binding protein 2 (SATB2) immunohistochemistry (IHC) has high sensitivity and specificity for colorectal adenocarcinoma (CRC), but data on its expression in specific subsets of pulmonary, gastric, small bowel, and pancreatobiliary adenocarcinomas (ADCAs) are relatively limited or discordant. We assessed SATB2 expression in a large cohort of ADCAs from these sites to determine its reliability in distinguishing CRC from them.<bold>Methods: </bold>SATB2 IHC was performed on 335 neoplasms, including 40 lung ADCAs, 165 pancreatobiliary neoplasms (34 intraductal papillary mucinous neoplasms [IPMNs], 19 pancreatic ADCAs, 112 cholangiocarcinomas [CCs]), and 35 gastric, 13 small bowel, 36 ampullary (AMP), and 46 CRC ADCAs. The cases were evaluated for positivity (defined as ≥5% nuclear staining), and an H-score was calculated based on the percentage of SATB2+ cells and staining intensity. Analysis was performed to determine the optimal H-score threshold to separate CRC and non-CRC.<bold>Results: </bold>SATB2 was positive in 3% of lung, 2% of CC, 17% of gastric, 38% of small bowel, and 6% of AMP ADCAs. All pancreatic ADCA/IPMNs were negative, and 87% CRCs were positive.<bold>Conclusions: </bold>SATB2 is not entirely specific for colorectal origin and can be expressed in a subset of gastrointestinal ADCAs. It is most useful in the differential of CRC vs lung and pancreatobiliary ADCAs. [ABSTRACT FROM AUTHOR]