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.

Cytotoxic T cell infiltrates and tumoral PD-L1 expression in lymph node metastases from patients with cSCC of the head and neck were analyzed.

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.

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.