Breast cancer during pregnancy of Luminal A type overexpressed CXCL13

Pregnancy‐associated breast cancer has been increasing. In this study, we analyzed patients with breast cancer that occurred during pregnancy (PrBC) and compared their genetic profiles with those of patients with breast cancer that did not occur during pregnancy, within 1 year after childbirth nor during lactation (non‐PrBC). We performed gene expression analyses of patients with PrBC and non‐PrBC using microarrays and qRT‐PCR. Microarray analysis showed that 355 genes were upregulated in the luminal‐type PrBC group compared to those in the non‐PrBC group. The C‐X‐C motif chemokine ligand 13 (CXCL13) gene was the most upregulated in the PrBC group compared to that in the non‐PrBC group, especially in the luminal A‐type (p = 0.016). This result was corroborated by the qRT‐PCR analysis of microdissected cancer cells (p