ADH is a neoplastic proliferation that shares some characteristics of ductal carcinoma in situ (DCIS), but falls short quantitatively or qualitatively.  ADH is associated with a moderately increased risk of developing an invasive breast carcinoma (4-5x relative risk, 13-17% lifetime risk).

 

The morphology is similar to DCIS, but the findings do not entirely fill the duct spaces and/or don’t fulfill a quantitative size requirement for DCIS (some require 2 mm lesion).  In biopsy specimens it is important to perform an excision biopsy/lumpectomy because approximately 1/3rd of cases will have an associated higher grade lesion in the immediate vicinity (e.g. DCIS or an invasive carcinoma).