Allelic loss on chromosome band 18p11.3 occurs early and reveals heterogeneity in breast cancer progression

We examined the stage specificity and heterogeneity of 18p11 alterations in a series of tumors representing 96 microdissected samples. Significant los s of heterozygosity (LOH) (63%) was found, with 56% occurring early in duct al carcinoma in situ. Although most cases indicated LOH was clonally inheri ted, heterogeneity for 18p LOH occurred in 27% of tumors. When compared wit h other LOH data, 18p LOH was found in conjunction with allelic deletion on 3p, 9p, 17p and 17q, while 13q, 16q, and 11p were less frequently associat ed. These analyses suggest chromosome 18p11 alteration is a common and earl y event in breast disease.