A large 6q deletion is a common cytogenetic alteration in fibroadenomas, pre-malignant lesions, and carcinomas of the breast

To assess whether early breast lesions are the precursors of invasive carci nomas, three classes of breast lesions, namely benign tumors (including fib roadenomas), putative premalignant lesions (including cases of atypical hyp erplasia), and invasive carcinomas, were compared at the cytogenetic and mo lecular cytogenetic levels, Genetic relatedness was clearly demonstrated by the sharing of several anomalies, among which 6q deletions outnumbered all of the other alterations detected. Indeed, deletions of the long arm of ch romosome 6, most likely occurring in epithelial cells, were present in 83.9 % of benign breast tumors, 64% of putative premalignant lesions, and 77.4% of analyzable carcinomas. Furthermore, the interval between 6q24 and qter a ppeared to be the common region of deletion in all three classes of breast lesions, whereas the minimal common region of deletion was 6q27-qter. Inter estingly, the latter region was reported previously to be deleted in benign ovarian tumors and recently found to barber a gene (SEN6) that is importan t for SV40-mediated immortalization of human cells.