FOLLICULAR DENDRITIC CELL-SARCOMA - CLINICOPATHOLOGICAL ANALYSIS OF 17 CASES SUGGESTING A MALIGNANT POTENTIAL HIGHER THAN CURRENTLY RECOGNIZED

BACKGROUND. The goal of this study was to characterize the clinicopath ologic features of follicular dendritic cell sarcoma, a very uncommon neoplasm. METHODS. The 17 cases were collected from the consultation a nd surgical pathology files of the authors, including 8 previously rep orted cases. The histologic and immunohistochemical features and outco me were analyzed. RESULTS. The patients had a median age of 40 years, with a slight female predominance. Seven patients presented with enlar ged lymph nodes, and ten presented with tumor in extranodal sites. Two cases were associated with hyaline-vascular Castleman's disease. The tumors had an average greatest dimension of 6.7 cm. The most common hi stologic feature was a storiform or fascicular array of spindle, ovoid , or polygonal cells with Oval nuclei, delicate nuclear membrane, vesi cular or granular chromatin, distinct nucleoli, indistinct cell border s, and frequently fibrillary cytoplasm. There were often scattered mul tinucleated forms. The tumor cells sometimes formed sheets, circular w horls, follicle-like structures, trabeculae, or pseudovascular spaces. There was a sprinkling of small lymphocytes, with or without cuffing around blood vessels. The neoplastic cells were immunoreactive for CD2 1 (17 of 17 cases), CD35 (17 of 17 cases), desmoplakin (10 of 17 cases ), epithelial membrane antigen (14 of 16 cases), S-100 protein (6 of 1 7 cases), and CD68 (2 of 17 cases), but not cytokeratin. Ultrastructur al studies showed villous processes connected by desmosomes. Only one harbored the Epstein-Barr virus. Among 13 patients with a median follo w-up of 3 years, local recurrence occurred in 6, metastasis in 6, and 3 died of disease. CONCLUSIONS. Follicular dendritic cell sarcoma exhi bits distinctive histologic features that permit its presumptive recog nition, but a firm diagnosis requires confirmation with special studie s. Because it has a significant recurrent and metastatic potential (th e latter risk having been previously underestimated), it should be vie wed as an intermediate grade malignancy. An intraabdominal location is associated with a particularly aggressive clinical course. (C) 1997 A merican Cancer Society.