The intimate histologic relationship of pregnancy-like hyperplasia (PLH) and cystic hypersecretory hyperplasia (CHH) has been previously reported. However, none of these published cases contained coexisting carcinoma. In this study, we describe 9 additional cases of this lesion, all of which also revealed ductal carcinoma in situ (DCIS) as well as invasive carcinoma in 1 case. Hematoxylin and eosin-stained slides were reviewed for all cases. All were women who ranged in age from 35 to 49 years (mean 42.0 years; median 42.5 years). Reasons for surgical biopsy were calcifications in 6, breast mass in 2, and nipple discharge in 1. One patient with a mass also experienced nipple discharge. Three women initially underwent needle core biopsy and 6 had an excisional biopsy. Six women ultimately had mastectomies. Histologically, 5 had CHH merging with coexisting PLH. Atypia was seen in one or both components. All 9 cases contained DCIS. Two cases showed micropapillary DCIS, one of which appeared to arise from atypical PLH, while 4 of the 7 cases containing cystic hypersecretory DCIS appeared to arise from coexisting atypical CHH. Well-differentiated invasive carcinoma was identified in 1 case adjacent to cystic hypersecretory DCIS. Subsequent sentinel lymph node biopsy in this case revealed micrometastatic disease. Clinical follow-up was obtained in 9 patients and ranged from 10 to 69 months. All patients were free of disease at the time of last follow-up. Careful clinical follow-up is recommended for lesions that display atypia in PLH, CHH, or a histologically combined lesion. If these lesions are found on a needle core biopsy specimen, an excisional biopsy is recommended. DCIS, usually micropapillary or cystic hypersecretory types, and rarely invasive carcinoma can arise in this setting. Affected patients are typically younger than those with more common types of breast carcinoma.