Evolution of immune infiltration and immune triad formation across early melanoma progression

T cell and dendritic cell densities, immune triad density, and triad proximity to melanoma cells are elevated in Stage I invasive melanoma versus Stage 0 in situ lesions and nevi.

• Why it matters: It is unclear when immune recognition of transformed melanocytes begins and how it changes during early melanoma progression, limiting how TIL-based prognostic signals are interpreted.
• What they did: Using spatial transcriptomics on a patient-matched cohort spanning multiple early evolution stages, the study quantified T cells, DCs, and multi-cell immune triads and tested whether triad abundance tracked with cell clustering at larger spatial scales.
• The result: Triad abundance correlates with both T cell and DC density, but is not predicted by broader-scale clustering patterns; depth-matched nevi show that the Stage I increase is not explained by dermal invasion alone.

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