TDO2 and neoplasm: To uncover underlying mechanisms, we integrate bulk and single-cell RNA sequencing and identify a preferential enrichment of interleukin 4 induced 1 (IL4I1)-expressing tumor-associated macrophages (TAMs) and tryptophan 2,3-dioxygenase (TDO2)-expressing myofibroblastic cancer-associated fibroblasts (myCAFs) in a solid pattern of LUAD.