Given the aberrant GPC1 expression in solid tumors and its unique role in tumor progression, a number of studies have explored the diagnostic and prognostic value of GPC1 in certain tumor types, including pancreatic cancer [14, 15], breast cancer [16], prostate cancer [17], colorectal cancer [18, 19], glioblastomas [6, 20], esophageal squamous cell carcinoma (ESCC) [21] and NSCLC [22, 23]. This evidence concerns the gene GPC1 and breast cancer.