Validation of HNF1B expression in normal mid-secretory endometrium. A, Expression z-scores averaged from all probes for ESR1 and HNF1B on an external microarray-based dataset (GSE4888), validating expression of HNF1B in mid-to-late secretory phase. B, IHC staining of endometrium at various menstrual cycle phases for HNF1B. Control specimens used are tissues from endometrioid endometrial carcinoma (negative) and clear cell carcinoma of the ovary (positive) that have been previously described as being negative or positive for HNF1B (respectively). These were rerun in the same experimental lot as endometrium samples. Note that stromal cells further serve as internal negative control in the CCOC control specimen as staining is restricted to nuclei of tumor epithelium. C, Tabulation of HNF1B IHC results from a panel of 12 normal endometrium samples shows segregation by menstrual cycle phase. D, HNF1B IHC results from Human Protein Atlas, with two different antibodies, for two normal endometrium samples at the secretory phase showing strong staining for HNF1B.