Unicentric Castleman disease treated with rituximab before surgery: clinicopathologic findings.

Castleman disease (CD) is a rare lymphoproliferative disorder with unique clinicopathological features, including two distinct clinical subtypes categorized as unicentric (UCD) and multicentric (MCD). UCD usually involves a single lymph node site presenting with no or minimal local symptoms. Histologically, most UCD cases exhibit regressive hyaline vascular germinal centers, characterized by penetrating vessels, dendritic hyperplasia/dysplasia, and increased interfollicular vascularity. While complete surgical excision is the standard treatment for UCD, cases treated with neoadjuvant anti-CD20 therapy have been reported. Here, we describe a UCD case treated with anti-CD20, that showed only a partial response. We detail the clinical findings and the histological changes observed in the surgical specimen following therapy, and discuss the potential influence of the local microenvironment on the therapeutic efficacy of anti-CD20.