Fine-needle aspiration biopsy findings in a case of follicular dendritic cell tumor

Follicular dendritic cells (FDCs) are non-lymphoid immune accessory cells found in follicles of lymph nodes. Tumors purported to arise from FDCs have recently been described and are considered rare. Histologically, these tumors show an admixture of large, spindled cells and benign lymphocytes. The large cells display a syncytial growth pattern, have delicate chromatin, and, in part, are defined by their expression of complement receptors. The authors recently observed the fine-needle aspiration (FNA) cytologic findings in a case that was subsequently proven to be a FCD tumor. Direct smears exhibited a dimorphic cellular pattern composed of large pale cells admixed with small lymphocytes. The large cells had delicate chromatin, inconspicuous nucleoli, and nuclear membrane infoldings, including occasional cytoplasmic protrusions into the nucleus. The cells were arranged singly and in syncytial groups. These cytologic findings may be characteristic enough to suggest the diagnosis of FDC tumor. Immunocytochemical confirmation should be sought in such cases.