The genomic profile of double primary secretory breast carcinoma in one patient provides evidence for the treatment of such carcinoma: A case report.

Secretory breast carcinoma (SBC) is one of the rarest breast carcinomas and currently lacks a standard treatment regimen. To date, few reports on double primary SBCs have been published, especially regarding the tumors' genomic features. A 51-year-old woman with early SBC who developed a secondary SBC in the contralateral mammary tissue 140 months later was evaluated. Here, we describe for the first time the sequencing results of a Chinese patient with nonsimultaneous double-primary SBC. In addition to the ETV6-NTRK3 fusion, variants in polymorphisms of enzymes related to drug metabolism variant genes, including BCL2L11, CYP2B6, CYP2C19, ERCC1, GSTM1, GSTP1, MTHFR, NQO1, TYMS, and XRCC, were present according to 425-gene DNA sequencing. The ETV6-NTRK3 fusion site was different between the tumors; furthermore, whole-gene exon sequencing revealed that genetic variation spectrum of the two tumors was different. A POLDIP2 mutation was found in the first tumor, and HDLBP, MMP2, PLEKHA6 and ZNF285 variants were detected in the second tumor. Our findings further our understanding of the molecular pathogenesis of SBCs, especially regarding tumors occurring at different times in one patient. Further molecular analyses of such cases are warranted to improve targeted therapies for SBC.