Fine-needle aspiration findings in Castleman's disease.

Castleman's disease of the hyaline vascular subtype is an uncommon lesion; experience with fine-needle aspiration (FNA) of this tumor is limited to rare case reports. We describe the cytologic, flow cytometric, and immunohistochemical findings in two cases initially sampled by FNA. Two females, aged 40 and 26 yr, were found incidentally to have an oropharyngeal and a mediastinal mass, respectively. Neither complained of systemic symptoms, and both had a normal routine laboratory workup. FNA followed by surgical excision in both cases was consistent with Castleman's disease of the hyaline vascular type. In the appropriate clinical context, a mature small lymphoid population associated with larger atypical cells, which are consistent with follicular dendritic cells, can be suggestive of Castleman's disease. Confirmation of a polytypic B-cell population by flow cytometry, supported by immunohistochemistry, is very helpful. However, definitive distinction from Hodgkin's lymphoma on FNA is probably not possible.