SIGMAR1 and breast cancer: In a study conducted on 109 normal, benign, and cancerous breast tissue specimens to determine SigmaR1 expression level in breast cancer by using immunohistochemistry and qRT-PCR, SigmaR1 mRNA overexpression was present in 60% of invasive cancers, 41.5% of in situ cancers, 75% of ductal hyperplasias, and 33% of normal breast tissue [33].