Issues

A digitized image of a hematoxylin and eosin-stained breast tissue section represents a benign diagnostic breast biopsy specimen largely comprised of adipose tissue and with marked terminal duct lobular unit (TDLU) involution. TDLUs are the structures responsible for lactation and are also the histologic source of most breast cancers. TDLU involution, a normal process of aging, is characterized by a reduction in the number and size of TDLUs and their secretory substructures called acini. In this image, rare ducts and equivocal acini are present, but well-developed TDLUs are not identified. Involution of TDLUs has been associated with lower mammographic density and reduced breast cancer risk. See the article by Gierach and colleagues (beginning on page 149) for more information.