Interleukin-6 transcripts up-regulation in lymph nodes from unicentric and multicentric Castleman disease.

Introduction: Castleman disease (CD) represents a spectrum of heterogeneous lymphoproliferative disorders sharing peculiar histopathological features, clinically subdivided into unicentric CD (UCD) and multicentric CD (MCD) and presenting with variable inflammatory symptoms. Interleukin (IL)-6 and other cytokines play a major role in mediating CD inflammatory manifestations. Although the local microenvironment seems to be among the major sources of hypercytokinemia, the precise cellular origin of IL-6 production in CD is still debated. Methods: A series of five nodal CD of different subtypes (one UCD, two idiopathic MCDs [iMCDs], one HIV-negative human herpesvirus 8 (HHV8)-associated MCD, and one HIV-positive HHV8-associated MCD) and a non-CD reactive control were tested using RNAscope analysis and a dual in situ hybridization (ISH)/immunohistochemistry technique, in order to quantify IL-6 expression and its spatial distribution. Quantitative analyses of in situ mRNA were performed on digitalized slides using the HISTOQUANT software (3DHISTECH) and differences between cases were evaluated by the Kruskal-Wallis test. Results: RNA-ISH documented increased Conclusion: Our findings suggest that nodal IL-6 expression seems to be significantly upregulated in HHV8+ MCD, but a trend toward increased nodal IL-6 expression was noticed also in UCD and iMCD-not otherwise specified. CD31+ endothelial cells probably represent one of the major sources of IL-6 production in the nodal microenvironment.