Follicular dendritic cell sarcoma arising in the dura mater of the spine.

There have been some individual case reports and a few large series of reports describing the clinicopathologic features of follicular dendritic cell sarcoma. This tumor originates from the dendritic cells of lymphoid follicles and is extremely rare in the extranodal location. We report the case of a 68-year-old man who presented with low back pain. A mass was found in the lumbar dura mater and extended to the right epidural space. The tumor was composed of nodules, sheets, and interlacing fascicles of oval-to-spindle cells intermingled with the dense infiltrates of small lymphocytes. Immunohistochemical staining revealed that the tumor cells were positive for CD21, CD23, CD35, and clusterin, and focally positive for CD68, CD20, and CD79a. To our knowledge, this is the first case of follicular dendritic cell sarcoma occurring in the dura mater of the spine.