Distinguishing maculopapular immune-related adverse events (irAE) from conventional drug eruptions (DE) can be difficult because of overlapping clinicopathological features. In this single-centre retrospective cohort, the proportion of PD-1-positive cells among CD3-positive T cells (PD-1/CD3%) showed complete separation between groups and may provide an objective adjunct to routine histopathological assessment. This simple metric may support clinicopathological attribution and inform management decisions in patients receiving immunotherapy.
Ikuno et al. (Sat,) studied this question.