ESR1 and ductal breast carcinoma in situ: In 50% of the cases where tissue blocks from the same serum donor were available to determine PLAC1 expression by IHC, 92% of DCIS, 97% of ER+/PR+/HER2- and 100% of HER2+ and TNBC cancers expressed PLAC1 (Table 2, Fig 2A).