The ability to culture malignant breast cells is crucial to the success of many scientific studies. However, short-term cultures of breast cancers are composed predominantly of DNA diploid cells, leading to doubt regarding the presence of bonafide cancer cells in these cultures. Morphology by conventional light microscopy is not helpful since cultured benign cells take on features usually associated with malignancy. In this study we examined by image analysis both benign and malignant breast cancer cells before and after culture. Consistent changes in both benign and malignant cells were found following culturing. There also were consistent differences distinguishing the cultures derived from benign and malignant specimens. While the features used were not sufficiently powerful to identify individual cells or cultures as benign or malignant, our results strongly suggest that malignant breast cells do indeed grow in short-term cultures.