Background: Castleman's disease is a rare disorder of lymphoid tissue that occurs chiefly in the mediastinum and less commonly at other sites, including the retroperitoneum. Few cases of fine needle aspiration (FNA) findings of this lesion have been reported.
Case: A 21-year-old man presented with left-side abdominal pain of 2 months' duration. A solid, well-defined pelvic mass measuring 7.2 x 4.3 x 5.3 cm displacing the urinary bladder and blood vessels was seen on ultrasonography. Ultrasound-guided FNA was performed; smears consisted predominantly of clusters of mature lymphocytes in hemorrhagic background showing crashing at places and closely intermingled with a distinct population of large follicular dendritic cells. Many clusters were seen traversed by capillary fragments. Cell block preparation showed concentric rings of mature lymphocytes surrounding lymphocyte-poor centers with vascular proliferation and follicular dendritic cells. Immunohistochemical staining of cell block sections showed leukocyte common antigen and CD20 positivity in small lymphocytes. A diagnosis of Castleman's disease was rendered, taking into consideration cytologic features and cell block findings. Subsequent histopathology confirmed the diagnosis.
Conclusion: A definitive diagnosis of Castleman's disease on FNA is possible by a combination of cytologic features and cell block technique with an appropriate use of immunohistochemistry.