The invention relates to a simple screening test for neoplasia, a precancerous condition, or cancer of the breast. A method is described whereby a breast cancer marker is detected in breast fluid. In a particular embodiment, the method involves treating samples of breast fluids with an aldehyde detecting reagent without any prewashing. The appearance in breast fluids of a marker that is detected by an aldehyde detecting reagent, such as a Schiff's reagent, correlates very well with the disease status of the breast cancer subjects from which the fluids were obtained. Screening test kits are also provided.