Pregnancy-like (pseudolactational) hyperplasia: a primary diagnosis in mammographically detected lesions of the breast and its relationship to cystic hypersecretory hyperplasia.

Pregnancy-like (pseudolactational) hyperplasia (PLH) has long been recognized as an incidental finding in breast biopsies performed for various clinically detected benign and malignant conditions. The histologic features of PLH have been well described, including some instances exhibiting cytologic and structural atypia. The presence of calcifications in these lesions was rarely mentioned and was considered to be of little consequence. More recently, however, calcifications in PLH have become the target of needle localization and needle core biopsies. The authors report 12 instances in which PLH was the primary diagnosis in biopsy specimens obtained for radiographic abnormalities, usually calcifications. Six of 12 procedures (50.0%) were performed for mammographically detected calcifications, four cases for a mass, one for an "abnormal mammogram," and one for galactorrhea. Calcifications were present in PLH in 10 biopsies, in benign terminal ducts in one specimen, and were not identified histologically in the remaining specimen. In most instances, calcifications associated with PLH had smooth round or lobulated contours and distinctive, internal, unevenly spaced laminations. Cystic hypersecretory hyperplasia (CHH) was present in five specimens. In four of the five specimens, CHH merged with PLH (PLH/CHH). Four of 12 specimens (33.3%) showed atypia within foci of PLH/CHH. PLH should be recognized as a primary diagnosis in breast biopsies for mammographically detected abnormalities such as calcifications. Some calcifications associated with PLH have a distinctive histologic appearance, and their recognition can aid in the diagnosis of PLH. Additional cases of PLH/CHH must be studied to ascertain the clinical significance, if any, of this previously undescribed entity. The precancerous significance of PLH/CHH and of PLH with atypia has not been determined. In most instances, surgical excision would be prudent if PLH/ CHH or PLH with atypia is present in a needle core biopsy specimen.