The noteworthy phenomenon was that SPP1 was expressed higher in one subtype, such as M-S1 (cluster 0) in BC; M-S3 (cluster 2) in CRC; M-S1 (cluster 0) and M-S2 (cluster 1) in LC; M-S1 (cluster 0) and M-S5 (cluster 4) in OV; M-S2 (cluster 1) in PDAC; and M-S3 (cluster 2) in SCC, which were universal across six cancer types (Figure 2B and Supplementary Table 2). This evidence concerns the gene SPP1 and breast cancer.