Fine needle aspiration cytology in follicular dendritic cell sarcoma: a report of two cases.

Since the first description of extranodalfollicular dendritic cell sarcoma in 1994, there has been a gradual increase in understanding of the morphologic features and clinical presentation of this tumor. However, difficulties persist in making cytologic diagnosis.Two cases of follicular dendritic cell sarcoma with fine needle aspiration cytology (FNAC) findings were reported. The first patient was a Chinese woman who presented with a right tonsillar mass, which was followed by right submandibular recurrence. The second patient was a Chinese man with known history of Castleman's disease of the nasopharynx complicated by follicular dendritic cell sarcoma, followed by tumor recurrence in cervical lymph nodes. FNAC of both recurrent cases showed isolated or syncytial sheets of tumor cells containing eosinophilic granular cytoplasm, ill-defined cell borders, round to oval nuclei, solitary round eosinophilic nucleoli and fine chromatin.The tumor cells in follicular dendritic cell sarcoma show cytologic features reminiscent of native follicular dendritic cells but with a greater than expected cell number and nuclear pleomorphism. These cells may be immunohistochemically inert for follicular dendritic cell markers CD21 and CD35. A presumptive diagnosis on the basis of cytologic examination is possible when paying attention to the subtle morphologic features.