Cutaneous squamous cell carcinoma (cSCC) is one of the most common types of human cancer which can metastasise. Dysfunctional immunity promotes cSCC development and anti-PD-1 immunotherapy can provide effective anti-tumour activity in advanced/metastatic cSCC. Tertiary lymphoid structures (TLSs) containing B-cells, T-cells and dendritic cells have been described in melanoma and other cancer types, and associate with improved clinical outcome and responses to anti-PD-1. However, the presence and role of TLSs in cSCC has yet to be determined. In this study, immunofluorescence microscopy was performed to quantify TLSs in formalin-fixed paraffin-embedded primary cSCCs which had metastasised (P-M, n=39) and primary cSCCs which had not metastasised (P-NM, n=47). TLSs, identified as clusters of immune cells >60,000 µm2 containing CD20+ B-cells, DC-LAMP+ dendritic cells and CXCL13+ cells, were observed in 33.7% of cSCCs, and were mainly situated in the stromal and peritumoral areas but in some cases were also noted in the surrounding skin. Although high CD20+ B-cell frequencies were associated with longer time to metastasis, there were no significant associations between the presence or numbers of TLSs with metastatic outcome and patient survival. There were no significant differences in tumour depth, diameter, and differentiation between TLS-positive and TLS-negative cSCCs. CD8+TCF1+ T-cells, which reside around TLSs and enhance anti-tumour immunity in other cancers, were detected in frozen cSCC sections (n=18 tumours), comprising 0.62% of the immune infiltrate, with no significant difference in CD8+TCF1+ T-cell frequencies between high and low risk cSCCs. Our data demonstrates that although a proportion of primary cSCCs contain TLSs, their presence does not affect clinical outcome in this tumour.

ESDR449 - Identification of tertiary lymphoid structures in primary cutaneous squamous cell carcinoma

The scientific meeting of the European Society for Dermatological Research (ESDR) is held yearly, usually in September. With an international attendance of more than 1000 skin scientists from around the globe, the four-day event includes short oral presentations from peer-reviewed abstracts, keynote lectures from international experts, sponsored symposia, satellite programs, educational events as well as an important focus on posters, networking and building collaborations amongst scientists. For more information about this year’s meeting visit our website.