KLK3 and prostate adenocarcinoma: Additionally, in some rare cases, the immunohistochemical assessment may reveal negative results for PSA, NKX3.1, and p501s, which are commonly used biomarkers for prostatic adenocarcinoma and showed a positivity for synaptophysin and chromogranin A that indicates adenocarcinoma of the prostate with neuroendocrine differentiation [92].