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 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 percentage of histiocytes with granules does not correlate significantly with the prognosis of these patients.