Somatic alterations in MUC4, QRICH2 and PR1L1 were identified in at least three of our breast MECs, which also existed in breast invasive carcinoma databases (TCGA, Cell 2015; TCGA, Nature 2012) and had no relationship with salivary gland MEC [25, 26]. Here, MUC4 is linked to invasive breast carcinoma.