One of the most satisfying experiences, for both surgeon and patient, is the withdrawal of a small amount of cloudy fluid from a discrete mass in the breast followed by the discovery that the lump which had terrified the patient has completely disappeared. Breast cyst aspiration is a safe, painless, inexpensive way to differentiate a benign breast lesion from a potentially malignant one. It shows immediately whether the lesion is really cystic and not dangerous or solid and possibly malignant. If a cancer should be growing inside the cyst, aspiration would reveal the presence of bloody cyst fluid. If a cancer should grow in the cyst wall rather than in the cyst lumen, withdrawal of the cyst fluid not only would fail to make the mass disappear, but it would make the nodularity of the cancer more apparent. In addition to these diagnostic advantages of breast cyst aspiration, there is