SATB2 is a sensitive marker for lower gastrointestinal well-differentiated neuroendocrine tumors.

Special AT-rich sequence binding protein-2 (SATB2) is selectively expressed in the lower gastrointestinal tract mucosa and has been identified as a sensitive marker for colorectal adenocarcinomas. The goal of this study was to investigate the expression of SATB2 in well-differentiated neuroendocrine tumors to explore its potential as a diagnostic marker for hindgut well-differentiated neuroendocrine tumors. Immunohistochemical staining with a monoclonal antibody to SATB2 was performed on full tissue blocks in 167 well-differentiated neuroendocrine tumors of various origins. The staining was semi-quantitatively scored as 0 (no tumor cell staining), 1+ (1-25%), 2+ (26-50%), 3+ (51-75%) and 4+ (76-100%). Positive SATB2 staining was seen in 17% foregut (14/84, 12/66 primary and 2/18 metastatic), 12% midgut (3/22, 3/18 primary and 0/7 metastatic), and 90% hindgut (52/58, 44/49 primary and 8/9 metastatic) well differentiated neuroendocrine tumors. Most hindgut well-differentiated neuroendocrine tumors (41/58) showed 4+ staining. The specificity of SATB2 for foregut, midgut and hindgut well-differentiated neuroendocrine tumors was 34%, 54% and 84%, respectively. Our results indicate that SATB2 is a sensitive marker for hindgut well-differentiated neuroendocrine tumors though it is not entirely specific. SATB2 should be included in the immunohistochemical panel in working out metastatic well-differentiated neuroendocrine tumor of an unknown origin.