Resection is an effective treatment for recurrent follicular dendritic cell sarcoma from retroperitoneum: unusual presentation of a rare tumor.

Retroperitoneum follicular dendritic cell sarcoma (FDCS) is an extremely rare neoplasm. The treatment of this disease is not clear. A 49-year-old Chinese female who had been found a 4.4×4 cm retroperitoneum mass by routine physical examination was received radical resection. Pathology revealed an inflammatory pseudotumor-like follicular dendritic cell tumor. After five years follow-up, a new nodule was noted on the tail of pancreas by routine CT evaluation. Re-resection was performed and pathological examination found a spindle-cell tumor with a great quantity of froth histiocytes. Immunohistochemical stains were positive for CD35 and CD21 which suggested it was a recurrent FDCS. Retroperitoneum FDCS is a very rare tumor. Surgical resection may be the first choice for this disease, even for recurrent tumor, if feasible. A relatively good prognosis often is achieved when compared with other malignancy.