Castleman disease. Histopathological and immunohistochemical analysis of 39 cases.

Introduction: Castleman disease (CD) is a rare lymphoproliferative that comprises two distinct clinical subtypes (unicentric and multicentric) and has two basic histopathology patterns that are hyaline-vascular (HV) and plasma-cell (PC) type. Some cases of multicentric PC disease are associated with HHV-8 infection.

Objective: To present the histopathologic and immunohistochemical characteristics of 39 cases of CD.

Methods: A review of cases with the diagnosis CD from the files of the Department of Pathology of the ABC Medical Centre in Mexico City was performed. Thirty-nine cases of CD were identified, and a detailed paraffin immunophenotypic study of 9 of them was completed using desmin, cytokeratin OSCAR (CO) and Epidermal growth factor receptor (EGFR), to evaluate the dendritic cell population.

Results and Conclusions: Of the 39 cases of CD, 24 were HV and 15 CP. All HV cases were unicentric and only one case of CP was multicentric. The most frequent localization in both subtypes was in lymph nodes; 21/24 cases in HV and 15 cases of CP. All cases were immunostained with CD20 that was expressed in the germinal centers (CGs), CD3 in the paracortical zone, and CD21 in follicular dendritic cells (CDF) within CGs, with expansion towards the area of the hyperplastic mantle zone (only in the HV variant). One case of CD CP was positive for HHV-8. Of the nine cases (6 HV and 3 PC cases) that were detailed with IHC, we found EGFR expression in FDC in all but one of the 9 cases studied and desmin was positive in fibroblastic reticulum cells (FRC) in all, but one of the cases of CD. CO was positive FRC in 3 of 6 cases of HV type and all (3) of the PC type. Clinical, histopathological and HIV and HHV-8 status markers, allow for the classification of CD into groups with markedly different outcomes and disease associations.