Development and validation of a predictive model for portal-systemic venous invasion grading in borderline resectable pancreatic cancer

Table 1 Distribution of pathological venous invasion outcomes (n = 167)

Grade	Definition	Cases
No invasion	Tumor cells are confined to the perivascular connective tissue surrounding the vein but do not penetrate the adventitial layer	39
Adventitial invasion	Tumor cells are confined to the adventitial layer of the vein and do not breach the external elastic lamina or invade deeper structures of the venous wall	47
Muscularis propria invasion	Tumor cells invade and are present within the smooth muscle layer of the venous wall (muscularis propria/muscular layer)	41
Intimal invasion	Tumor cells penetrate through the endothelial cell layer (endothelium) of the vein, becoming directly exposed to the vascular lumen, or are attached to/floating within the lumen (with or without thrombus formation)	40