Expression of SERCA3 in normal breast structures. Luminal cells of acini strongly express SERCA3. Intensity of labeling is comparable to that of endothelial cells (Panel C, red arrows) or lymphocytes (Panel D, small green arrows). SERCA3 labeling in terminal duct luminal epithelium is very weak to weak (Panels A, B and C, large green arrows). In larger ducts SERCA3 labeling is somewhat more heterogeneous, and varies from weak to moderate (Panel D). Myoepithelial cells in acinar, as well as ductal structures are negative. Original magnification: ×20 (Panels A and B), ×40 (Panels C and D).