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Figure 4a. Gradually enlarging asymmetric tissue. Mediolateral views of the same breast (a) at baseline mammography, (b) at mammography 2 years later, (c) at mammography 6 years later, and (d) at mammography 9 years after baseline show the development and subsequent enlargement of benign-appearing asymmetric tissue (arrows in b–d) in the upper part of the breast. In a–c, the patient is premenopausal. The patient was asymptomatic and refused to undergo biopsy at the time the mammogram in b was obtained. (d) The postmenopausal mammogram shows a decrease in density of both the asymmetric tissue and the parenchymal tissue.