Pathology of histiocytic disorders and neoplasms and related disorders

Abstract

The pathology of histiocytic disorders and neoplasms of the macrophage-dendritic cell lineages is heterogeneous and may have overlapping features, all the while made more difficult by their rarity. The morphologic features together with immunophenotype and pattern of involvement should be taken together with the clinical and radiographic findings to make a unifying diagnosis. The "molecular microscope” of these lesions is further unraveling their biologic potential, which in some cases has helped to solidify their standing as inflammatory myeloid neoplasms. The histopathologic clues for the diagnosis of Langerhans cell histiocytosis (LCH), Erdheim-Chester Disease (ECD), the "juvenile xanthogranuloma” (JXG) family of lesions, Rosai-Dorfman disease (RDD), malignant histiocytoses including histiocytic sarcoma and Langerhans cell sarcoma, and other less common histiocytic-related disorders, including hemophagocytic lymphohistiocytosis (HLH), are reviewed in this chapter.