In our previous expression profiling study of 14 novel primary breast cancer cell lines of varying histological grade (grade 1: n = 3; grade 2: n = 7; and grade 3: n = 4) developed in our laboratory, and 51 breast epithelial cell lines established by others [16], BST2 was among the most highly expressed genes in grade 3 tumor lines identified by Significance Analysis of Microarrays (SAM). Here, BST2 is linked to breast carcinoma.