Transformation of Castleman's Disease into Follicular Dendritic Cell Sarcoma, Presenting as an Asymptomatic Intra-abdominal Mass

Follicular dendritic cell (FDC) sarcoma is an extremely rare malignant neoplasm arising from FDCs. The exact origin of FDCs remains unclear; both a hematopoietic lineage origin and a stromal cell derivation have been proposed. Proliferation of FDCs can lead to benign reactive lesions or generate neoplastic conditions. The lesions are most commonly found in lymph nodes and usually involve the head and neck area. Castleman's disease is a rare non-neoplasitic lymphoproliferative disorder. Rare cases of hyaline-vascular Castleman's disease have been associated with FDC sarcoma, but a clonal relationship has not been convincingly demonstrated. A pathway toward tumor evolution, beginning with hyperplasia and dysplasia of FDCs, has been proposed. Despite this known association between Castleman's disease and FDC sarcoma, there have only been few reported cases of sarcoma arising as a complication of pre-existing Castleman's disease, especially in abdominal lesions. We describe here a 51-year-old female with an FDC sarcoma arising from unicentric, hyaline-vascular type Castleman's disease in an intra-abdominal mass. Pathologically, the lesion showed a series of changes during the process of transformation from Castleman's disease to FDC sarcoma. (Korean J Gastroenterol 2013;62:131-134).