ESR1 and breast cancer: Previously, we found that SPAG5 was upregulated in PLNM-positive tumor tissues: 15/23 PLNM-positive patients had high SPAG5 expression (65.217%) compared with 4/64 PLNM-negative patients (6.154%).2 Two other microarray profiling studies mentioned the SPAG5 upregulation in estrogen receptor-positive breast cancer and non-small-cell lung cancer,14, 15 but there have been no specific studies.