Programmed cell death ligand‐1 and cytotoxic T cell infiltrates in metastatic cutaneous squamous cell carcinoma of the head and neck

Background Metastatic cutaneous squamous cell carcinoma (cSCC) carries a poor prognosis. Increased numbers of CD8+ cytotoxic T cells are associated with a favorable prognosis and programmed cell death receptor‐1 is a suppressor of the CD8+ cytotoxic T cell response. We aim to define their expression in metastatic cutaneous squamous cell carcinoma. Methods Cytotoxic T cell infiltrates and tumoral PD‐L1 expression in lymph node metastases from patients with cSCC of the head and neck were analyzed. Results High tumoral PD‐L1 expression, intratumoral and peritumoral CD8+ cell density in metastases were significantly associated with poor primary tumor differentiation. Low PD‐L1 expression, intratumoral and peritumoral CD8+ density were associated with lower grade primary tumor differentiation. Low PD‐L1 expression correlated with disease progression. Conclusions Increased expression of PD‐L1 correlates with increased CD8+ cell density. Increased expression of PD‐L1 in poorly differentiated tumors may be more likely to benefit from anti PD‐1/PD‐L1 therapy.