Two benign epithelial breast lesions showing clonal chromosomal alterations involving 12q13-15 are reported. As the only clonal aberration a t(12;14)(q13-14;q24) was noted in a florid epithelial hyperplasia with extended adenosis. A t(10;12)(p14-15;q13) was found in a papilloma also with areas of florid epithelial hyperplasia.