Antigenic phenotype of Langerhans cell histiocytosis: an immunohistochemical study demonstrating the value of LN-2, LN-3, and vimentin.

In order to determine the antigenic phenotype of the proliferating cells in Langerhans cell histiocytosis (LCH), we studied 15 such examples by using formalin- and B5-fixed, paraffin-embedded tissues. We used a panel of antibodies that are known to react with lymphocyte- and histiocyte-associated antigens. These included LN-1, LN-2, and LN-3 monoclonal antibodies (MoAbs), MoAbs to leukocyte common antigen (LCA), Leu-M1 antigen, vimentin, and epithelial membrane antigen (EMA), as well as polyclonal antibodies to lysozyme and S100 protein. The antigens encountered most frequently in LCH cells were S100 protein (93% of cases), vimentin (86%), and those detected by LN-2 (80%) and LN-3 (82%). Lysozyme was detected focally in two cases and diffusely in one case. The LCH cells were negative for LN-1, LCA, Leu-M1, and EMA. There was only one specimen in which S100 protein was not demonstrated; in this case, LN-3, vimentin, and T6 on frozen section were positive. The phenotype of LCH cells is similar to that of Langerhans' cells and interdigitating histiocytes. Our results demonstrate the value of using a panel of antibodies, including anti-vimentin MoAb, LN-2, and LN-3 for the immunophenotypic diagnosis of LCH in addition to an antibody to S100 protein.