Fibrocystic disease is the most common type of lesion in the female breast. It is a common dumping ground for a variety of distinct clinical and histologic entities which require different modalities of therapy and which have different malignant transformation potentials. In general, fibrocystic disease is managed medically unless a dominant lump or other adverse symptom develops, in which case a biopsy is performed. The exception to this rule is a cyst which can be safely aspirated under controlled conditions. If, on biopsy, one of the histologic types of fibrocystic disease called "precancerous mastopathy" is found, which has a high potential for malignant transformation, then serious consideration must be given to definitive surgical procedures, especially if the patient has other risk factors that would increase her risk of developing breast cancer even further.