Primary and secondary intralymphatic histiocytosis.

Intralymphatic histiocytosis (IH) is a rare condition often associated with systemic disease. A benign condition, clinical presentations can vary greatly and its cause is largely unknown. Histologically, there are macrophages within distended lymphatic vessels, although this can be an incidental finding or the primary abnormality.We present a series of 7 cases of IH with and without disease associations, and a review of the literature. We propose IH as either primary (without associated conditions) or secondary (associated with systemic disease).This was a retrospective collection of patients whose skin biopsy specimens revealed intralymphatic collections of histiocytes. We reviewed their clinical presentation, disease associations, and staining of slides with CD68 in all cases, D2-40 in 5 cases, and HLA-DR in 4 cases.Clinical features were highly variable, and not all cases were associated with systemic disease. One case had admixed reactive angioendotheliomatosis. All 4 cases stained for HLA-DR showed strong expression by the intralymphatic macrophages.Retrospective analysis and limited numbers are limitations.IH is not always associated with systemic disease although macrophage activation nevertheless implies immune activation.