Editorial: Immune-related biomarkers in skin and breast cancer: innovations in immunological diagnostics and therapies

Non-melanoma skin cancers and breast cancer underscore the same problem from different biological angles. Merkel cell carcinoma (MCC) and cutaneous squamous cell carcinoma (cSCC) are immunotherapy-responsive tumors, with durable activity of PD-1/PD-L1 blockade, high pathological response rates after neoadjuvant cemiplimab in cSCC, and emerging evidence that systemic inflammation may shape outcome. Breast cancer is more heterogeneous: triple-negative and HER2-positive tumors are usually more immune enriched than hormone receptor-positive disease; pathological complete response is prognostically informative; checkpoint inhibition improves outcomes in selected patients. Across these settings, biomarkers must therefore move beyond association and become decision tools for treatment selection, escalation or de-escalation, early response monitoring, toxicity prediction and treatment discontinuation.