ESR1 and breast carcinoma: However, it is worth noting that similar occurrences have been witnessed with other cell lineage-specific transcription factors, such as microphthalmia-associated transcription factor (MITF) in melanoma,45 androgen receptor (AR) in hormone-independent prostate cancer,46 estrogen receptor alpha (ESR1) in breast cancer,47 and more recently, NK2 homeobox 1 (NKX2-1, also known as thyroid transcription factor-1/TITF-1) in lung cancer.48