FACTOR XIIIA EXPRESSION IN JUVENILE XANTHOGRANULOMA

Dermal dendrocytes constitute the largest population among cells of de rmatofibromas. In other histiocytic tumours, the exact nature of histi ocytic cells is not known. We have searched for the presence of dermal dendrocytes in juvenile xanthogranulomas. The immunohistochemical stu dy was performed on 9 juvenile xanthogranulomas. We used monoclonal or polyclonal antibodies: anti-XIIIa, HAM56, anti-S100, anti-NSE, anti-H LA-DR, anti-CD68 and anti-lysozyme. Phagocytic mononuclear cells (hist iocytes, giant cells, Touton cells) did not express Langerhans' cell m arkers (S100, NSE ou HLA-DR). They weakly expressed markers of macroph ages (CD68, lysozyme). There was a very strong binding by HAM56 and an ti-XIIIa. This expression was more evident on xanthomatous and newly a ppeared tumours than on fibrous tumours. The largest population of juv enile xanthogranuloma cells appeared to be constituted by dermal dendr ocytes. These cells are perhaps the key-cells of a continuum of benign tumours, from juvenile xanthogranuloma to dermatofibroma, with differ ent stages corresponding to different proportions of dendrocytes, lymp hocytes and fibroblasts.