POU1F1 and adenoma: However, IHC for PIT1 (pituitary-specific positive transcription factor 1; coded by the POU class 1 homeobox 1 gene), SF1, TPIT (coded by the T-box transcription factor 19 gene), and estrogen receptor-α (ERα) allowed for the identification of mutually exclusive lineage-specific markers in 95% of the cases, reducing the prevalence of the null cell adenoma subtype to ~1% (10) (Fig. 4C and 4D).