AR and cancer: Neuroendocrine transdifferentiation (NEtD), also commonly referred to as lineage plasticity, emerges as an acquired resistance mechanism to molecular targeted therapies in multiple cancer types, predominately occurs in metastatic epidermal growth factor receptor (EGFR)‐mutant non‐small cell lung cancer treated with EGFR tyrosine kinase inhibitors and metastatic castration‐resistant prostate cancer treated with androgen receptor targeting therapies.