Intracytoplasmic and extracytoplasmic features of secretion, similar to lactational changes, occasionally are seen in the nonparous human breast, usually are lobulocentric, and often have aberrant cytologic and nuclear changes. In these "hypersecretory hyperplasias" (HHs; 38 women) there is bubbly cytoplasm with irregular apical cytoplasmic and/or nuclear protrusions. In a review of 138 HH cases the following additional associated changes were found: nuclear atypia (HHA, 22 women), atypical ductal hyperplasia (ADH-HH, 24 women), and ductal carcinoma in situ (DCIS-HH, 54 women). A diagnosis of DCIS-HH requires involvement of true duct(s) and of several contiguous lobular units, emphasizing the importance of extent and overall size and similar cytology and histologic arrangement of intercellular spaces indicating a homogeneous cell population. Cases of HH regularly are characterized as having adjacent and nearby lobular units with quite diverse cytologic patterns. The major impact of this study is to recognize that HHA may be regarded as having uncertain significance when found alone in the usual presentation in a single unit, but that formally defined ADH and/or DCIS may be locally present.