This study is designed to look at whether it is feasible to observe women with atypical ductal hyperplasia (ADH) of the breast, or whether surgical excision is necessary.

We hypothesize that surgical excision may not yield an improvement in survival over hormonal therapy and/or close observation alone in patients who present with ADH on core needle biopsy of the breast. An alternate (non-inferior) strategy for management may be possible, and may be associated with improved quality of life and fewer complications, and lower overall costs. Although several researchers have suggested a clinical trial to investigate this idea this would be the first time it has been done, and could therefore be practice changing.

Inclusion Criteria

A patient/subject is eligible for enrollment if all of the following inclusion criteria are met:

1. Pre- and post-menopausal women ≥ 40 years of age with newly diagnosed ADH, histologically confirmed on breast core biopsy.
2. Ability to understand and the willingness to sign a written informed consent document.
3. Willing to schedule definitive resection of ADH if randomized to surgical excision arm or be observed if randomized to the observation arm.
4. Original breast core biopsy specimen available for pathologic review and staining by Yale School of Medicine Department of Pathology.

Exclusion Criteria

A patient/subject will not be eligible for this study if any of the following exclusion criteria are met:

1. Patients with a current breast cancer diagnosis or a personal history of cancer
2. Patients with a personal history of an identifiable genetic mutation (BRCA) for breast cancer and, untested first degree relatives of mutation carriers
3. Patients who have previously or are currently taking tamoxifen or exemestane or other chemotherapy or biologic therapy (e.g. trastuzumab)
4. Patients with a history of radiation therapy to the chest wall
5. Pregnant and/or lactating women within past 6 months.

Patients presenting to the Breast Clinic at Smilow for evaluation and management of ADH will be identified. After screening and informed consent, patient demographics and study specific data points will be obtained by interview and chart review. Patients will then be randomized to surgical excision or close observation.