Intraabdominal follicular dendritic cell sarcoma - Report of a case with fine needle aspiration findings

BACKGROUND: Follicular dendritic cell sarcoma is a rare tumor derived from dendritic cells of lymphoid follicles. Although it shows characteristic cytologic, histologic and immunohistochemical features, it may be misdiagnosed because of the lack of experience with this entity. There are few reports in the cytologic literature describing this entity. CASE: A left hypochondrial mass was found in an 80-year-old man who had a past history of colonic carcinoma. A computed tomography-guided fine needle aspiration biopsy was performed, and the findings were initially thought to be compatible with metastatic carcinoma. The mass was excised, and a diagnosis of follicular dendritic cell sarcoma was made. CONCLUSION: Follicular dendritic cell sarcoma is characterized by loosely cohesive or syncytial groups of dendritic cells that show oval, vesicular nuclei and ill-defined cytoplasm intimately admixed with small, mature lymphocytes. The diagnosis can be confirmed by positive immunostaining for CD21 and CD35 antigens and negative staining for cytokeratin. Unusual features in our case were the presence of prominent plasma cells and intracytoplasmic, periodic acid-Schiff stain, diastase-positive deposits, with the last not described before.