Deciphering the full spectrum of Castleman diseases based on a cohort of 700 patients in a western country.

Under the Castleman disease (CD) eponym, three distinct diseases sharing common pathological features have been described over time. Using the French national registry for CDs, we revisited the full spectrum of these diseases to update our current knowledge on the optimal management of these patients. The unicentric type (UCD) has usually an indolent course and can be cured by surgical resection. However, a small percentage of the UCD patients develop severe autoimmune or malignant complications. The human herpesvirus 8 (HHV8)-associated multicentric type (HHV8+ MCD) has been mainly described in human immunodeficiency virus (HIV)-infected patients but is an emerging condition outside this setting in other populations. The third type, idiopathic multicentric Castleman disease (iMCD) remains a challenging diagnosis as the pathological features observed in these patients are shared with many other conditions such as lymphoid neoplasia and systemic diseases. Other syndromes such as POEMS (polyneuropathy, organomegaly, endocrinopathy, M-protein and skin changes), TAFRO (thrombocytopenia, anasarca, myelofibrosis, renal dysfunction and organomegaly), IgG4-RD (IgG4-related disease) and IPL (idiopathic plasmacytic lymphadenopathy) may also overlap with iMCD and could be considered either associated conditions or differential diagnosis. In addition, the clinical phenotype of iMCD exhibits several striking differences among populations with a much more heterogeneous pattern in Western populations than in patients of Asian ancestry.