Disseminated histiocytosis X. A clinical and immunohistochemical retrospective study.

Fourteen cases of disseminated histiocytosis x (HX) from a 15 year period were studied clinicopathologically. Morbidity and mortality were comparable to that of previous reports on disseminated HX. S-100 protein, recently established as a HX marker, was demonstrated immunohistochemically in the cytoplasm and the nuclei of the HX cells of 12 examined cases. Neuron specific enolase (NSE) positive material was found in a minority of the cells of 2 cases. Cytoplasmic lysozyme was present in the mononuclear cells accompanying the HX cells in all examined cases. These results show that immunohistochemical demonstration of S-100 protein and lysozyme can be successfully applied to formalin-fixed, paraffin embedded tissue after storage at room temperature for as long as 15 years. The presence of cytoplasmic NSE positivity in the lesions from 2 patients was surprising and has not previously been observed in HX. This finding suggests an antigenic heterogenicity between cases with the disease of unknown prognostic significance. Nor did the presence of lysozyme in the lesions from patients with acute as well as chronic disease yield any prognostic information.