Follicular Dendritic Cell Tumor in Castleman's Disease

Abstract

We report two cases of follicular dendritic cell tumor associated with Castleman's disease, one of the hyaline vascular type and one a mixed hyaline-vascular and plasma cell type. The reactive lymphoid follicles in both cases contained a proliferation of abnormal follicular dendritic cells characterized by enlarged, irregular contoured nuclei and prominent nucleoli (in-situ component). Both tumors had similar histology. They were vaguely fascicular and composed by eosinophilic, ovoid to spindled cells with vesicular nuclei and prominent nucleoli admixed with small lymphocytes. Some of these cells seen in the reactive follicles were similar in appearance to the ones seen in the adjacent invasive tumors. The association of follicular dendritic cell tumor with Castleman's disease and the presence of in-situ follicular dendritic cell tumor within reactive lymphoid follicles suggests that there may be a progression from dysplastic follicular dendritic cells to follicular dendritic cell tumor in Castleman's disease. The sequence of events and the likelihood that patients with Castleman's disease showing follicles with dysplastic changes will develop follicular dendritic cell tumors is not known at this time owing to the limited number of cases reported.