Bcl‐2‐positive epidermal dendritic cells in inverted follicular keratoses but not squamous cell carcinomas or seborrheic keratoses

Aim:  In our previous research, bcl-2-positive dendritic cells were seen in increased numbers in suprabasal areas of inverted follicular keratoses (IFKs) compared to seborrheic keratoses (SKs). The purpose of this study was twofold; firstly, to support that these dendritic cells are Langerhans cells and secondly, to contrast the epidermal dendritic cells in IFKs, squamous cell carcinomas (SCCs), and SKs. Methods:  Ten IFKs and five SKs previously showing bcl-2-positive dendritic cells within the epidermis were stained with CD1a. Fifteen other IFKs were stained with CD1a alone. Ten SCCs were stained with bcl-2 and CD1a. Results:  In the 10 IFKs stained with both bcl-2 and CD1a, the density of CD1a-positive cells correlated well with the density of bcl-2-positive dendritic cells; in the five SKs, the density of CD1a-positive cells was similar to that seen in IFKs but was higher compared to the density of bcl-2-positive dendritic cells in SKs (p < 0.05). The IFKs had a significantly higher number of CD1a-positive cells compared to SCCs (p < 0.01). SCCs showed bcl-2-positive cells only within the basal layer of the normal epidermis flanking the carcinomas. Conclusion:  These results suggest that there is different bcl-2 regulation of CD1a-positive cells in IFKs, SKs, and SCCs.