Difficulties in the fine needle aspiration (FNA) diagnosis of schwannoma.

The results of nine FNAs of eight histologically proven schwannomas are presented. In only one of the aspirates was a diagnosis of schwannoma made; three additional cases were diagnosed as 'spindle cell neoplasm'. Two of the cases were considered to be non-diagnostic due to hypocellularity, while two cases containing cellular material raised the differential diagnosis of granulation tissue and granulomatous inflammation due to the presence of epithelioid cells and an inflammatory infiltrate, and are illustrated here. The remaining FNA was felt suggestive of branchial cleft cyst due to the presence of only cystic fluid in a neck mass. We observe that: (i) the acquisition of an adequate, representative specimen via FNA is often difficult in schwannoma, and (ii) diagnostic difficulties may be encountered in cases in which cellular material is obtained.