A flow cytometric study of Langerhans cell histiocytosis.

Langerhans cell histiocytosis (LCH), or histiocytosis X, is now generally considered to be a non-malignant condition. A flow cytometric (FCM) study of a single case has, however, been published which claimed to provide evidence to contradict this. The presence of DNA-ploidy as detected using this technique is a feature of malignant and pre-malignant disease. In this reported single case, DNA-ploidy was present but the clinical features of this patient were atypical for LCH. We have performed a FCM study of the DNA of nine biopsies of LCH lesions from six patients with well-established disease. In addition, in one of these, fresh tissue studies including the use of an anti-CD I monoclonal antibody to specifically label the LCH cells were performed. In all cases the DNA content of the cells was entirely normal. We therefore found no evidence that LCH is a neoplastic disorder.