D2-40 labelled LMVD with IHC staining (200×). A-C Invasive ductal breast cancer: A. Stained lymphatic microvessels within a peripheral tumor (long arrow) with dilated tubes. Capillary vessel (short arrow) and tumor cell clusters were not stained; B. The central-tumor vascular structures appear linear, small and flattened, cluttered and densely arrayed; C. a cluster of tumor cells (arrow) in a stained vessel, or "tumor emboli". D. Luminal epithelial cells with D2-40 negative staining. Myoepithelial cells from normal ducts and lobules had positive D2-40 immunostaining (short arrow), but with a granular, branching membranous staining pattern that is distinct from the characteristic staining pattern of lymphatic endothelium (long arrow). E-F Metastatic lymph nodes: E. stained lymphatic microvessels in the metastasis, with irregular lumens and cracked tube walls; F. dilated lymphatic microvessel sub-capsular metastasis with no staining of tumor cells within it; defined as lymphatic vessel invasion (LVI) (arrow).