Immunohistochemical study on 26 cases of Langerhans cell histiocytosis (LCH) using several leukocyte antibodies in addition to traditionally used markers (S-100 protein and peanut agglutinin) revealed that the proliferating cells of LCH expressed UCHL1, MT1 as well as classically known positivity for S-100 protein, HLA-DR and peanut agglutinin but were negative for OPD4.
Lung biopsy showed fibrosis of the interalveolar septa, architectural distortion and large cells with foamy cytoplasm and convoluted nuclei that were marked by CD68, S-100 and the specific antibody CD1a that allowed establishing the diagnosis of pulmonary LCH.
The inguinal node biopsy revealed a multinodular proliferation of large cells S100 and CD1a<sup>+</sup>, and a diagnosis of Langerhans cell histiocytosis was made.
Immunohistochemistry shows positivity for S100 and CD1a in Langerhans-cell histiocytoses (LHCH) of the L group, while CD68 positivity with S100 and CD1a negativity are typical in histiocytoses of the C group of cutaneous and mucocutaneous histiocytoses.
In biopsy, pathological examination of Langerhans cells were observed with positive S-100 protein and Ki-67 antigen markers, findings were sufficient to establish a diagnosis of central nervous system (CNS) LCH.
These large histiocytic cells with vesicular nuclei and nuclear grooves were immunopositive for CD1a and S100, concluding the diagnosis of Langerhans cell histiocytosis.