Cytogenetic studies of benign breast lesions

Abstract: In the present thesis benign breast lesions of various histologies, i.e., fibrocystic lesions from women with and without a known hereditary predisposition to breast cancer, fibroadenomas, phyllodes tumors, and papillomas were cytogenetically investigated with the aim to characterize the chromosomal patterns, and to relate the findings with those in breast carcinomas. No lesion-specific aberration was detected; on the contrary, changes repeatedly encountered in short-term cultures from breast cancer samples were found in these benign entities as well, e.g., gain of 1q, interstitial deletion of 3p, and trisomies 7, 18, and 20, and some cases even displayed cytogenetic polyclonality. Especially intriguing is the prevalence of rearrangements of the short arm of chromosome 3, with the minimally deleted bands 3p13-14, in proliferative lesions from prophylactic mastectomies in breast cancer families. The potential tumor suppressor gene(s) in this region remains, however, to be identified. In general, the frequency of benign cases with chromosome abnormalities is lower compared to breast cancer, and seems to correlate with the histologic features of the tissue, and the corresponding risk of developing invasive mammary carcinoma. The anomalies are generally less complex than those detected in invasive carcinoma, and more often involve balanced rearrangements. Furthermore, the degree of cytogenetic complexity seems to correlate with the description of a phyllodes tumor as benign or malignant: malignant phyllodes tumors have a more complex karyotype.