ESR1 and ductal breast carcinoma in situ: Despite that the first FFPE block used in our study (Sample #1; Figs. 1–5) was annotated by a pathologist as HER2 + /ER + /PR−, we found a region of DCIS that was positive for the RNA of all three receptors, in just one 5.5 mm × 7.5 mm section of the much larger biopsy (Fig. 5).