Proliferative disorders of histiocytes consist of a broad spectrum1 of lesions, which range from rapidly progressive ones that disseminate widely and behave as malignant neoplasms to those that are limited to a single site, grow slowly, have a limited capacity for extension into adjacent tissues, and are considered benign. A subset of lesions, so-called histiocytosis X,2-4 is rendered somewhat more complex by the fact that while there is little morphologic variation among the lesions, their biologic behavior may vary significantly. Although much has been written about the various clinical variants of histiocytosis X, there is considerable overlap, and they are sufficiently uncommon that their prognosis is not always predictable. Nor are there predictive morphologic markers as shown by a recent review5 that reports that the presence of cytoplasmic laminated bodies or convoluted membranous profiles called "wormlike" bodies do not correlate with a "selfhealing"
Scarpelli DG. Histiocytosis X. Arch Dermatol. 1986;122(4):402-403. doi:10.1001/archderm.1986.01660160058017