LANGERHANS CELL HISTIOCYTOSIS OF THE HYPOTHALAMUS - DIAGNOSTIC-VALUE OF IMMUNOHISTOCHEMISTRY

The immunophenotype of 6 cases of Langerhans cell histiocytosis (LCH) of the hypothalamus and 3 cases of cranial bone manifestation of LCH w as investigated by means of immunohistochemistry on paraffin sections. Antibodies against S 100 protein, lysozyme, CD68 (PG-M1), CD68 (KP1), HLA-DR, beta(2) microglobulin, placental alkaline phosphatase (FLAP), the monoclonal antibody MAC 387, and a monoclonal antibody against CD 1a were used, All examined cases showed positive staining of lesional cells for S 100 protein, HLA-DR, beta(2) microglobulin, macrophage ass ociated markers and CD1a. According to the ''confidence levels'' of th e Writing Group of the Histiocyte Society [Chu et al. 1487], a ''defin ite diagnosis'' of LCH requires the demonstration either of Birbeck gr anules in lesional cells by electron microscopy, or of CD1a antigenic determinants on the surface of lesional cells. Since electron microsco py of these rare CNS lesions is not possible in many cases, we are now able to give a definite diagnosis of LCH of the hypothalamus by means of immunohistochemistry for CD1a on routinely fixed and processed tis sue.