Proliferation and dilation of acini is evident with a concurrent decrease in the intralobular stroma. Other stromal changes include increased vascularity with an infiltration of inflammatory cells. Note that there are secretions present inside the lumen of the ectatic acini.
This image demonstrates a vascularized stroma with inflammatory cells. The epithelial cells lining the lumens have hyperchromatic nuclei and vacuolated cytoplasm. The enlarged epithelial cells protrude into the lumen, creating a
During the first trimester of pregnancy, the terminal ductal lobular unit grows rapidly. There is a proliferation of ducts and lobules with a concomitant decrease in the fibrofatty stroma. The reduction of stroma is most evident within intralobular stroma.
In the second and third trimester, proliferation of the lobules continue, and the epithelial cells becoming increasingly large, vacuolated, with hyperchromatic nuclei and prominent nucleoli. The glandular lumens will also continue to accumulate secretions. Changes become most pronounced in the lactating/nursing breast, with lobules containing almost back-to-back glands and large vacuoles (containing milk) clearly evident within the enlarged epithelial cells.
Rosen PP. Rosen's Breast Pathology. 3rd Ed. Philadelphia: Lippincott Williams & Wilkins; 2009:12-14.