Representative images of immunohistochemical staining with PD-1 and TIGIT (A) Several strong PD-1 positive TILs (left, black arrows, broken line) next to single weakly stained tumour cells (right, black arrows, continuous line). (B) Weak PD-1 positive solid growing tumour cells (upper half of picture, black arrows, continuous line) and strong PD-1 positive TILs (lower half of picture, black arrows, broken line). (C) Non-neoplastic, TIGIT negative bronchial tissue cells (left) and strong TIGIT positive lung adenocarcinoma tumour cells with lepidic growth pattern (right). (D) Numerous strong TIGIT positive TILs (black arrows, broken line) infiltrating TIGIT negative highly differentiated acinar growing lung adenocarcinoma tumour (black arrows, continuous line).