Diagnosis: Follicular dendritic cell sarcoma (FDS)
Follicular dendritic cell sarcoma tumors, which most often occur in the head and neck, are rare and frequently misdiagnosed. First recognized in 1986 by Monda et al,1 FDS has recently become more well described and therefore more frequently diagnosed. Dendritic cells are nonlymphoid, nonphagocytic cells that capture, process, and present antigens to B cells on their cell membranes. The 4 types of dendritic cells are interdigitating, indeterminate, Langerhans, and follicular dendritic.2 The latter cells are located in germinal centers of lymphoid follicles; therefore, most of these tumors (70%) develop within lymph nodes. The other 30% develop extranodally in acquired lymphoid tissue. The most frequent sites of extranodal involvement in the head and neck are the tonsil, pharynx, palate, and thyroid (in decreasing order of frequency). Follicular dendritic cell sarcoma is not isolated to the head and neck, as it has also been found in the liver, lung, spleen, pancreas, breast, and gastrointestinal tract.3 It appears to affect males and females equally, mostly in the fifth and sixth decades of life.