Active Surveillance of Atypical Ductal Hyperplasia of the Breast.

Background: When needle core biopsy (NCB) of the breast yields atypical ductal hyperplasia (ADH), excision is typically recommended. The natural history of ADH undergoing active surveillance (AS) is not well described. We investigate the rates of upgrade to malignancy of excised ADH and the rates of radiographic progression under AS.

Materials And Methods: We retrospectively reviewed records of 220 cases of ADH on NCB. Of patients who had surgery within 6 months of NCB, we examined the malignancy upgrade rate. In the AS cohort, we examined rates of radiographic progression on interval imaging.

Results: The malignancy upgrade rate among patients who underwent immediate excision (n = 185) was 15.7%: 14.1% (n = 26) ductal carcinoma in situ (DCIS) and 1.6% (n = 3) invasive ductal carcinoma (IDC). Upgrade to malignancy was less common in lesions <4 mm in size (0%) or with focal ADH (5%), and more common among lesions presenting with a radiographic mass (26%). Among the 35 patients who underwent AS, median follow-up was 20 months. Two lesions progressed on imaging (incidence 3.8% at 2 years). One patient without radiographic progression was found to have IDC at delayed surgery. The remaining lesions remained stable (46%), decreased in size (11%), or resolved (37%).

Conclusions: Our findings suggest that AS is a safe approach to managing ADH on NCB for most patients. This could spare many patients with ADH from unnecessary surgery. Given that AS is being investigated for low-risk DCIS in multiple international prospective trials, these results suggest that AS should also be investigated for ADH.