Chromosomes of benign and malignant lesions of the breast

Four cases of benign cystic mammary disease, two cases of in-situ lobular carcinoma and eight cases of invasive mammary carcinoma are described. Benign lesions were studied both by tissue biopsy and nipple secretions. All showed normal diploid karyotypes. Carcinoma in situ presented predominantly normal diploid karyotypes but, because this lesion was seen in conjunction with benign cystic disease, both probably contributed to the metaphase spreads studied. One invasive tumor showed a normal diploid karyotype. The other seven were aneuploid. Tumors with multiple chromosomal abberations and with multiple modal numbers appear to be more aggressive. The role played by such factors is discussed.