Follicular dendritic cell sarcoma: a diagnostic challenge !

Follicular dendritic cell sarcoma (FDCS) is a spindle cell neoplasm of histiocytic-dendritic cells origin. It is known to occur in lymph nodes and rarely has been reported in extranodal tissues like head and neck, mediastinum and gastrointestinal tract. We herein report the first FDCS arising from anal canal in a 56-year-old man. The tumor was composed of bland short spindle cells in focal whorl formation with interspersed few lymphocytes. The tumor cells were classically positive for CD21, CD23, CD35 and vimentin. Despite its misleading morphology, immunohistochemistry helped us to reach a conclusive diagnosis for relevant therapy.