ESR1 and ductal breast carcinoma in situ: When DCIS-only samples were separately analyzed, expression profiles tended to be higher (compared to invasive tumor), exceeding the generally accepted intra-run variation of 0.70 cycles in 18/22 cases for ERBB2 (81.8%), in 19/22 cases for ESR1 (86.4%), in 14/22 cases for PGR (63.6%) and in 11/22 cases for MKI67 (50.0%).