High IL1R2 expression indicated a poor prognosis in BC patients. A) The most upregulated/downregulated genes among the common deregulated genes in BTICs (B) and the rest non‐BTICs (R). B) Represent deregulated genes in 25 BC samples compared with 15 paratumor samples. C) IL1R2 was co‐upregulated in both BC samples and PDX BTICs. D) IL1R2 mRNA and protein (SUM149) were upregulated in BTICs compared to non‐BTICs sorted from two BC patient samples and BC cell lines (**, p < 0.01; *, p < 0.05). E) IL1R2 mRNA was upregulated in breast cancer patient tumor samples compared with paratumor tissue samples (*, p < 0.05; **, p < 0.01 vs paratumor group). F) IL1R2 protein expression was upregulated in the majority of patient tumor samples compared with the corresponding paratumor tissue samples (n = 38). Representative images were shown. Original magnification, 200×. G) IL1R2 expression was determined in four different molecular subtypes of BC patient samples by TMA analysis (n = 50/each subtype) (*, p < 0.05 vs the normal control) (representative images were shown). Original magnification, 100×. H,I) High IL1R2 mRNA expression indicated a shorter overall survival and relapse‐free survival rate in BC patients (analyzed as previous report38).