To date, the rare primary
histiocytoses of the skin are diagnosed definitively on the basis of the clinical symptoms, H&E-stained sections, and demonstration of CD1 positivity in frozen sections and of Birbeck granules on electron microscopy. The improvement and analysis of
antibodies with the ability to react in
paraffin tissue allow retrospective evaluation and classification of these disorders. The
antibodies for S-100-protein,
peanut agglutinin (PNA) and
PCNA (
proliferating cell nuclear antigen) have been advocated for differentiation of the specific cells of
Langerhans cell histiocytosis (LCH) from other histiocytic cell systems. To date the non-
Langerhans cell histiocytoses (non-LCH) have no common ultrastructural and immunohistochemical characteristics. The infiltrate is made up of multiple cell populations, which are of significance for the cellular pathobiology (subtypes of monocytes/macrophages and dendritic cells). The number and distribution of the different monocyte/macrophages and dendritic cells and their ability to react with immunohistochemical markers in
paraffin tissue can be completely different in different clinical entities. The
antibodies against
factor XIIIa (shown on
xanthoma disseminatum) and the
monoclonal antibody Ki-M1P (shown on
juvenile xanthogranuloma) seem to be valuable in discrimination between LCH and non-LCH. Both markers show a positive staining pattern with the characteristic large macrophages. In
juvenile xanthogranuloma, the foam cells and giant cells express Ki-M1P, KP1 and anti-
cathepsin B. Other monocyte/macrophage markers with the ability to react in
paraffin tissue, such as Mac387,
lysozyme,
alpha 1-antitrypsin and Leu-M1 (Anti-CD 15), in contrast, did not show a typical staining pattern with the characteristic large macrophages dominating the histological picture.