Achaete-scute homolog 1 expression closely correlates with endocrine phenotype and degree of differentiation in sinonasal neuroendocrine tumors

Primary sinonasal tumors with neuroendocrine differentiation (STNDs) are uncommon, with overlapping histology. According to the amount of neuroendocrine component, they can be subcategorized into esthesioneuroblastoma, high-grade sinonasal neuroendocrine carcinoma/small cell carcinoma, and sinonasal undifferentiated carcinoma. Achaete-scute homolog 1 (ASH1) is a master gene for neuroendocrine differentiation and is expressed in fetal and adult neuroendocrine tissues. Expression of ASH1 protein may be a useful marker for cancers with neuroendocrine features. The aim of this study was to compare and assess the value of ASH1 protein expression/levels in STND. We reviewed the morphological features and performed immunohistochemical analyses for ASH1 in 30 samples of surgically resected cancers with neuroendocrine differentiation from our institution. Achaete-scute homolog 1 was found to be expressed in STND, indicating that it is instrumental in the development of a subset of neurons and neuroendocrine cells and plays a key role in regulating neuroendocrine differentiation in tumor cells. Achaete-scute homolog 1 levels were associated with the degree of STND tumor differentiation (high-grade tumors show increased expression of this protein), correlating well with studies indicating that expression of ASH1 appears to be restricted to immature cells.