The definitions vary, but NCCN definition of borderline resectability for PCA are:
SMV/PV involvement (distortion, narrowing or occlusion) that can be resected and reconstructed using nearby vessels.
Tumor abutment on SMA ≤180 degrees, CHA abutment without extension to celiac axis or hepatic bifurcation.
Gastroduodenal artery encasement up to the hepatic artery, including up to short segment encasement or direct abutment of the hepatic artery, without celiac axis involvement.