This microenvironment encompasses a set of cellular and molecular components that form the context in which the tumor initiates, proliferates, and eventually infiltrates surrounding normal tissue and actively participates in communication that ultimately supports tumor progression.3 Recent evidence suggests a pivotal role of tryptophan (TRP) metabolism via the kynurenine (KP) and serotonin (SP) pathways in this intricate peritumoral interplay.4,5. Here, NPPA is linked to neoplasm.