Hoskoppal D, Epstein JI, Gown AM, et al. - Researchers investigated the expression of special AT-rich sequence-binding protein 2 (SATB2) in 266 neuroendocrine neoplasms (NNs) from various primary sites. In addition, they assessed its utility as a marker in determining the site of origin of these neoplasms. They performed SATB2 immunohistochemistry on NNs including lung small cell carcinomas (N = 39) and carcinoids (N = 30); bladder (N = 21) and prostate (N = 31) small cell carcinomas; and gastrointestinal (GI)/pancreatic NNs of various primary sites (N = 145) consisting of well-differentiated neuroendocrine tumors (N = 124) and poorly differentiated neuroendocrine carcinomas (PDNEC)s (N = 21). Receiver operator characteristic analysis suggests SATB2 as a sensitive and specific marker for rectal (100.0%; 80.0%) and appendiceal (100.0%; 84.5%) well-differentiated neuroendocrine tumors, respectively. Hence, it seems to be a valuable diagnostic tool when considering these sites of origin in the differential diagnosis.