KRT5 and neuroendocrine neoplasm: Increasing evidence supports the notion that these neuroendocrine tumor cells are different from their counterparts in the normal prostate gland, in terms of their cellular morphology and expression of lineage/tumor-specific markers including cytokeratin 5/18 and AMACR [36,41], indicating that neuroendocrine tumor cells are one type of bona fide epithelial constituent of prostate cancer (Figure 1).