ERBB2 and neoplasm: The stroma primarily localizes to interstitial spaces and is fibroblast-rich; the ductal epithelium consists of clustered ER+ cancer cells surrounding glandular structures; the periductal area is dominated by HER2+ cancer cells located adjacent to ducts; the stromal vascular region is enriched in vascular smooth muscle cells near blood vessels; and the immune infiltration region mainly comprises T-cells and macrophages, frequently found at tumor margins and areas of necrosis.