PD-L1 Expression, T-lymphocyte Subpopulations and Langerhans Cells in Cutaneous Squamous Cell Carcinoma and Precursor Lesions.

BACKGROUND/AIM: The role of immune cells and PD-L1 in cutaneous squamous carcinogenesis is unclear. This study examines T-cell populations, Langerhans cells (LCs) and PD-L1 in invasive squamous cell carcinoma (inSCC), adjacent precursors and normal skin (NS) to investigate their participation in tumorigenesis. MATERIALS AND METHODS: Cases of cutaneous inSCC with adjacent precursors (n=125) were selected. In situ SCC (isSCC) and actinic keratosis (AK) were observed in 53 and 123 cases, respectively, whereas NS was present in 123 lesions. Immunohistochemistry was performed for CD3, CD8, Foxp3, CD1a and PD-L1. RESULTS: T-cells, LCs and PD-L1 gradually increase during the evolution from AK to isSCC and inSCC, with statistical significance between all lesions, except for CD3+ and CD8+ cells between isSCC and inSCC. Epithelial PD-L1 expression correlates with tumor diameter and thickness. CONCLUSION: The progressive increase of T-cells, LCs and PD-L1 in cutaneous squamous carcinogenesis provides rationale for immunotherapy and identification of predictive biomarkers.

Evaluation of T-lymphocyte subpopulations in actinic keratosis, in situ and invasive squamous cell carcinoma of the skin.

BACKGROUND: Tumor infiltrating lymphocytes (TILs) represent important regulators of carcinogenesis. Cutaneous invasive squamous cell carcinoma (inSCC) develops through precursor lesions, namely in situ squamous cell carcinoma (isSCC) and actinic keratosis (AK), representing a natural model of carcinogenesis. The study evaluates TIL subpopulations in inSCC and its precursors by comparing 2 semiquantitative scoring systems, and assesses the presence of regulatory T-cells (Tregs) in these lesions. METHODS: Paraffin sections from 33 cases of AK, 19 isSCCs and 34 inSCCs with adjacent precursor lesions or normal skin (NS) were immunostained for CD3, CD4, CD8 and Foxp3. TIL subgroups were evaluated by the semiquantitative Klintrup-Mäkinen (K-M) score, and by a more detailed modification of this system. Treg counts were assessed by image analysis quantification. RESULTS: An increase of all TIL subpolulations from precursor lesions toward inSCC was shown by both scoring systems. Treg counts progressively increased from NS to AK and isSCC, but decreased in inSCC. Tregs were more numerous in pT2 and around indolent inSCCs compared to T1 and aggressive subtypes. CONCLUSIONS: T-cells and cytotoxic T-cells progressively increase in cutaneous squamous cell carcinogenesis, while Treg counts diminish in inSCC. The K-M score is an appropriate, easily applicable TIL scoring system in cutaneous inSCC.