are terms often used interchangeably among pathologists to describe the histologic finding of tumorcells within a vessel(Fig. 9–8). The term “vascular invasion” should be restricted to cases in which tumor cells areseen within a vessel con­taining a muscular wall (with or without red blood cells) and the term “lymphatic invasion” should be limited to evidence of intraluminal groups of tumor cells conforming to the shape of the endothelial-lined space. Whereas the for­mer is relatively rare, the latter is much more common. The term “lymphovascular invasion” should be limited to cases in which both are seen, but this is rarely the case in practice. In addition, the reproducibility of this finding is in question because it is often hard to tell the difference between lymphatic invasion and arti­fact. Immunohistochemical stains are emerging that will help differentiate true lymphatic inva­sion; this is important because this finding implies a higher chance of finding nodal meta­stases. Likewise, the finding of lymphatic or vascular invasion correlates with prognosis in node-negative patients, including decreased disease-free survival and increased local recur­rence after breast conservation therapy (BCT). Even though lymphovascular invasion is not a contraindication to BCT, its presence may influ­ence adjuvant chemotherapyand radiation ther­apy decisions.