Schwannomas: a pitfall in the diagnosis of pleomorphic adenomas on fine-needle aspiration cytology.

Fine-needle aspiration cytology (FNAC) is being employed with increasing frequency for the preoperative diagnostic workup of salivary gland lesions. Although most cases show morphologic features very characteristic of specific entities, few lesions, both benign and malignant, can cause problems in interpretation. We report four cases initially diagnosed on FNA as spindle-cell tumors, possibly benign nerve sheath tumors (BNST) in the salivary gland region. These cases were later diagnosed on histologic examination as schwannoma (two cases) and as pleomorphic adenoma (two cases). Review of the cytomorphology of these four cases enabled the correct diagnosis of pleomorphic adenoma in the two cases misinterpreted as BNST. Benign peripheral nerve sheath tumors should always be considered in the differential diagnosis of pleomorphic adenoma. A diligent search for epithelial elements is recommended prior to diagnosing BNST in the head and neck region. Copyright 2002 Wiley-Liss, Inc.