Castleman Disease and Rosai-Dorfman Disease.

ABSTRACT

This chapter describes the main features of two different diseases, Castleman Disease (CD) and Rosai-Dorfman Disease (RDD). Castleman disease (CD) is a clinical and histopathologically heterogeneous lymphoproliferative disorder that encompasses at least three distinct entities with some common overlapping morphological features Hyaline Vascular CD (HVCD), Unicentric Plasma Cell CD and Multicentric CD. The most important feature of HVCD is the presence of abnormal germinal centers with hyaline-vascular transformation, sometimes showing multiple germinal centers within a single reactive lymphoid follicle, this outlining HVCD as a disorder of follicular dendritic cells. Unicentric and multicentric CD are, in contrast, lymphoproliferative lesions. Proinflammatory hypercytokinemia is an essential feature of multicentric CD, distinguished by a florid clinical presentation. Rosai-Dorfmann Disease is a histiocytic proliferative disorder diagnosed by the presence of tissue infiltration by S100-positive CD1a-negative histiocytes and plasma cell aggregates, often with Russell bodies. A typical, though not specific, characteristic of the disease is emperipolesis. Initially considered to be an inflammatory/reactive condition, molecular studies suggest that at least some cases of RDD could be considered as a low-grade histiocytic neoplastic process.