Pathological characteristics and tumour immune microenvironment of lung malignancies with RET rearrangement

•M2 macrophage infiltration into the tumour parenchyma may have a better prognosis.•A novel KIF5B-RET (k24:R8) rearrangement in pulmonary sarcoma was first reported.•RET-fusion patients with high PD-L1 expression may be sensitive to immunotherapy.•The proportion of M2 macrophages in tumour stroma was higher than parenchyma.