Comparative genomic hybridization analysis of myoepithelial carcinoma of the breast

Although there seems to be a common stem cell for the two epithelial cell t ypes in the breast, the Vast majority of breast cancers exhibit a luminal p henotype. Pure myoepithelial carcinomas are rare. We report our findings of genetic alterations in these tumors. We have analyzed 10 cases of pure myo epithelial cell carcinomas using laser capture microdissection and comparat ive genomic hybridization. The mean number of changes was 2.1 (range 0-4), compared with a mean of 8.6 (range 3.6-13.8) in unselected ductal carcinoma s. Common alterations included loss at 16q (3/10 cases), 17p(3/10), 11q (2/ 10), and 16p (2/10), regions also commonly deleted in ductal carcinomas. Th e single case in which both pure myoepithelial carcinoma and invasive ducta l carcinoma was present showed 2 alterations in the myoepithelial tumor (lo sses at 17p and 17q), whereas the invasive ductal component showed 15 alter ations (5 gains and 9 losses), including loss at 17p. The sharing of 17p lo ss in myoepithelial and ductal carcinoma is consistent with a common stem c ell model in the breast. The relatively few genetic alterations in otherwis e aggressive neoplasms suggests that myoepithelial tumors may be a good mod el for the delineation of genes important in breast tumorigenesis.