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-mu m-thic k vertical skin sections, and confocal laser scanning microscopy (CLSM ) of 25-mu m-thick vertical sections. The use of CLSM enables both a q uantitative and a three-dimensional (3-D) analysis of the cells in the same tissue volume. A statistically significant reduction in the rela tive 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 reducti on in epidermal CD1a(+) cells was found in thin vertical sections. Thi s is probably due to the smaller tissue sample examined, and to variat ions in the number of CD1a(+) cells, with less cells directly overlyin g the tumour nests. The ratio of CD1a-expressing cells in the epidermi s/dermis was significantly reduced in BCCs, compared with healthy look ing skin. Few LCs were observed in tumour nests, but they were numerou s in the surrounding stroma of the dermis. Three-dimensional reconstru ctions of CD1a(+) cells in BCC revealed striking morphological changes ; they had a reduced number of dendrites, and these were often short a nd had few branches. The results demonstrate that CLSM is a suitable t echnique for quantitative and morphological analysis of CD la-expressi ng cells in the skin. We suggest that the alterations in LC numbers, d istribution and morphology in BCC most probably are secondary to chang es in the local environment.