EGF-like module containing mucin-like hormone receptor 2 (EMR2) is a leukocyte-restricted adhesion G protein-coupled receptor. Aberrant expression of EMR2 and its highly homologous molecule CD97 have been reported in various human cancers. Herein, we investigate the expression of EMR2 in neoplastic breast human tissue and its relationship with patient survival. EMR2 expression in normal and neoplastic breast tissue was assessed by immunohistochemistry in sections from 10 normal controls and micro-arrayed tissue cores from 69 cases of ductal carcinoma in situ (DCIS) and 272 invasive carcinomas. The pattern and intensity of staining was correlated with the clinicopathological characteristics of each case and the disease outcome. While absent in normal breast epithelium, EMR2 was significantly up-regulated in the cytoplasmic and nuclear compartments of both DCIS and invasive carcinoma, with invasive samples displaying significantly higher expression levels compared with in situ disease. In invasive disease, EMR2 cytoplasmic expression was significantly associated with higher tumour grade but not with patient age, nodal status, tumour size, estrogen receptor expression, relapse-free or overall survival. In contrast, EMR2 nuclear expression correlated negatively with higher tumour grade. Of note, EMR2 nuclear expression was associated with longer relapse-free survival as well as overall survival. This study indicates that EMR2 is expressed in neoplastic breast epithelium and suggests that expression patterns of EMR2 are relevant in breast cancer progression. The association of improved patient survival with higher nuclear expression levels identifies EMR2 as a potential biomarker in patients with invasive breast cancer.

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