Quantitative and 3-dimensional analysis of Langerhans cells in basal cell carcinoma. A comparative study using light microscopy and confocal laser scanning microscopy.

We have analysed Langerhans cells (LCs) in basal cell carcinoma (BCC) and in healthy skin in 15 patients, using three different techniques: light microscopic examination of horizontal sheets, and of 6-micron-thick vertical skin sections, and confocal laser scanning microscopy (CLSM) of 25-micron-thick vertical sections. The use of CLSM enables both a quantitative and a three-dimensional (3-D) analysis of the cells in the same tissue volume. A statistically significant reduction in the relative volume of epidermal CD1a reactivity confined to tumour areas was found with CLSM. This difference was confirmed when the number of LCs in horizontal sheets were counted. In contrast, no significant reduction in epidermal CD1a+ cells was found in thin vertical sections. This is probably due to the smaller tissue sample examined, and to variations in the number of CD1a+ cells, with less cells directly overlying the tumour nests. The ratio of CD1a-expressing cells in the epidermis/dermis was significantly reduced in BCCs, compared with healthy looking skin. Few LCs were observed in tumour nests, but they were numerous in the surrounding stroma of the dermis. Three-dimensional reconstructions of CD1a+ cells in BCC revealed striking morphological changes; they had a reduced number of dendrites, and these were often short and had few branches. The results demonstrate that CLSM is a suitable technique for quantitative and morphological analysis of CD1a-expressing cells in the skin. We suggest that the alterations in LC numbers, distribution and morphology in BCC most probably are secondary to changes in the local environment.