Elucidating the grading intricacies of idiopathic multicentric Castleman disease histopathology: a pathologist's perspective.

objectiveIdiopathic multicentric Castleman disease (iMCD) is a rare condition with a wide range of signs and symptoms that often overlap with other conditions that cause lymphadenopathy. The diagnosis of iMCD remains challenging, even among experts. Our aim is to highlight the heterogeneity of histopathologic features and presentations of iMCD and to provide tools to help diagnose and raise awareness of this rare condition.

methodsWe review the most relevant clinicopathologic aspects of iMCD and present our process to accurately diagnose this condition using a case-based approach. We describe how to incorporate the iMCD diagnostic criteria, including grading of histomorphology, laboratory, and clinical findings.

resultsHere, we describe our system to grade histopathologic features in iMCD. Together with radiologic findings and laboratory and clinical information, this system helps clinicians accurately identify iMCD and its subtypes, leading to more appropriate and timely diagnosis and treatment.

conclusionsThe diagnosis of iMCD can be challenging and requires a multidisciplinary team of hematologists, pathologists/hematopathologists, and other specialists. There is a pressing and unmet clinical need for a harmonized system to grade the histopathologic features of iMCD. This condition should be included in the differential diagnosis when other causes of a lymphoproliferative disorder (eg, infections, autoimmune/inflammatory disorders, malignancy) have been ruled out.