Breast carcinoma is a major cause of cancer mortality in women in the United States. At the advanced stages, breast carcinoma is characterized by genetic instability, loss of cellular architecture and glandular disorganization. However there is a lack of information about the mechanism that generates these cellular changes. Centrosomes are subcellular organelles regulate the mitotic spindle and control the fidelity of chromosomal segregation. Centrosome abnormalities may result in missegregation of chromosomes and genetic instability, a common feature of cancer cells. Centrosome defects have been described in invasive ductal breast carcinoma. However, it is not known how early these abnormalities occur in breast cancer. To address this the study was conducted to determine whether centrosomes are abnormal in ductal carcinoma of the breast DCIS. We analyzed semiquantitatively, the number, size and shape of centrosomes in paired normal lobules and DCIS lesions. Our study shows that centrosomes are abnormal in a significant fraction of DCIS lesions and suggest that centrosome dysfunction may be the cause of the chromosomal instability observed in DCIS. Our observations have important implications for the biology of breast cancer, that centrosome dysfunction are an early event in breast carcinogenesis and may be critical for cancer progression.