FoxP3-Positive Cells and Their Contacts with Mast Cells Are Highly Increased in Basal Cell Carcinoma.

INTRODUCTION: The cells of the immune system are thought to contribute to the development of skin cancers, such as basal cell carcinoma (BCC). One possible mechanism may be the interaction between mast cells and regulatory T cells (Tregs), resulting in immunosuppression. METHODS: Fresh-frozen biopsies from the lesional and nonlesional skin of 16 patients with BCC were processed for the enzymehistochemical staining of mast cell tryptase, immunohistochemical staining of FoxP3 (a marker of Tregs) as well as for the double-staining method to label tryptase+ cells and FoxP3+ cells on the same cryosection. The cell numbers and apparent morphological contacts (AMCs) between these cell types were counted. RESULTS: There was a high increase in the number of tryptase+ cells, FoxP3+ cells, and AMCs between them in the lesional compared to corresponding nonlesional skin (p < 0.0001) in all cases. CONCLUSION: A morphological basis is theoretically present in BCC, suggesting an immune evasive microenvironment.

CD40 Ligand Is Increased in Mast Cells in Psoriasis and Actinic Keratosis but Less So in Epithelial Skin Carcinomas.

The expression of CD40 ligand (CD40L) in mast cells was investigated in biopsies from lesional and non-lesional skin samples of patients with psoriasis, actinic keratosis (AK), basal cell carcinoma, and squamous cell carcinoma using a sequential double-staining technique. The percentage of CD40L+ mast cells was higher in the lesional than in the non-lesional skin (p < .003). Interestingly, this percentage was lower in both carcinomas than in psoriasis and actinic keratosis (p < .025). Cells immunopositive for CD40 receptor were increased in all lesion types but especially so in carcinomas. The results suggest a dysregulated anti-tumoral immune response by mast cell CD40L in skin carcinomas.