Lymphovascular Invasion

Definition

LVI usually relates to microscopic tumour emboli within small thin-walled channels in which distinction between post-capillary venule and lymphatic channel is not possible—hence the general term LVI is used. It is important to identify an endothelial lining to differentiate from retraction space artefact, which often comprises a rounded aggregate of tumour sited centrally and free within a tissue space. Other helpful features of LVI are red blood cells, thrombosis, a point of attachment to the endothelium and a paravascular location. In difficult cases endothelial markers (Factor VIII antigen, CD34, CD31) may be helpful but, in general, adherence to strict morphological criteria is recommended.

Significance

There is controversy as to the significance of LVI, but in practice most pathologists view tumours with prominent LVI as those that are most likely to show longitudinal submucosal spread/satellite lesions and lymph node involvement. Extratumoral LVI is regarded as more significant than intratumoral LVI and is most frequently encountered at the invasive edge of the tumour. LVI in tissue well away from the tumour is a strong marker of local and nodal recurrence in breast carcinoma, and is a criterion indicating the need for postoperative adjuvant therapy. When present in the overlying skin it denotes the specific clinicopathological entity of inflammatory breast carcinoma, which is staged pT4. LVI is a strong determinant of adjuvant chemotherapy in testicular germ cell tumours. LVI also forms part of the pT classification for testicular and liver tumours, and, if present in a distant organ (e.g. lymphangitis carcinomatosa of the lung in prostate tumour), it is classified as pM1.

Vascular involvement

Some tumours (hepatocellular carcinoma, renal cell carcinoma) have a propensity for vascular involvement and care should be taken to identify this on specimen dissection and microscopy as it also alters the tumour stage. Extramural vascular invasion is a significant adverse prognostic factor in colorectal carcinoma but can be difficult to define. Sometimes one is reliant on circumstantial evidence of a tumour-filled longitudinal structure with a wall partly formed of smooth muscle, lying at right angles to the muscularis propria and adjacent to an arteriole. Widowed arteries can be a useful indicator of venular involvement in a number of situations. The significance of vessel wall infiltration without luminal disease is uncertain, but probably indicates potential access to the circulation.

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