ELECTRON-MICROSCOPY IN HISTIOCYTOSIS-X

In an ultrastructural study of 24 cases of histiocytosis X, Langerhans cell granules were demonstrated in all 18 cases from which tissue had been submitted primarily for EM and in 4 of 6 cases from which only tissue retrieved from paraffin blocks was available for examination. In a subsequent correlative study, Langerhans cell granules were demonstrated in deparaffinized material from 11 of 14 cases (79%) in which they were known to exist. The incidence of histiocytes displaying Langerhans cell granules (in a single plane of section) fell from a median of 48% in samples processed primarily for EM to 14% in those retrieved from paraffin blocks. EM, even when applied to the study of suboptimally preserved material, is a highly sensitive technique for confirming a diagnosis of [human] histiocytosis X.