Retroperitoneal and mediastinal follicular dendritic cell sarcoma: report of 3 cases with review of literature.

Follicular dendritic cell sarcoma (FDCS) is a rare malignant histiocytic proliferation of antigen presenting follicular dendritic cell. It is an uncommon primary malignancy first described by Monda et al. in 1986. Most commonly reported cases are lymph nodal. Occasional cases occur in extra nodal sites. Here, we describe the clinicopathological features, histomorphology and outcome of three patients with extranodal FDCS along with a concise review of literature on the topic. All three patients were adult females. Two patients were in third decade, and one had age of 50 years. Among the three cases, two cases are presented as retroperitoneal mass and one as mediastinal mass. CT scans revealed heterogeneously enhancing masses. All the cases showed ovoid to spindle neoplastic cells arranged predominantly in whorling, fascicular and storiform patterns with inflammatory infiltrate. Immunohistochemically, the tumor cells are positive for CD21, CD23, CD35 and Clustrin. In view of rarity and variable clinical presentation in FDCS, accurate diagnosis is necessary.