Significance of X granules in histiocytosis X: an ultrastructural study.

Histiocytosis X is characterized by the presence of cytoplasmic rod structures called Langerhans' cell granules or X granules (XG). It has been speculated that histiocytosis X is a Langerhans' cell disorder. This ultrastructural study was performed to quantitate the number of XG containing histiocytes in the histiocytosis X lesions. Twenty-four specimens from 22 patients with histiocytosis X were studied: 4 from skin, 5 from lymph node, 11 from bone, 2 from lung, 1 from gingiva, and 1 from cheek. The majority of the histiocytes in histiocytosis X lesions do not contain X granules. The majority of the histiocytes in histiocytosis X lesions do not contain X granules. The percentage of histiocytes with XG in a lesion has no relation to the age of the patient or the organ from which it was obtained, except for skin, where they were quite numerous. The relative percent-age of histiocytes with granules does not correlate significantly with the prognosis of these patients.