CYTOLOGICAL FEATURES OF MALIGNANT METASTATIC AMELOBLASTOMA - A CASE-REPORT AND DIFFERENTIAL-DIAGNOSIS

In this report, the cytological features and differential diagnosis of the metastasis from and subsequent local recurrence of an unusual cas e of malignant (metastatic) ameloblastoma are described with histologi cal confirmation. Characteristic cytological findings included fibrova scular central cores surrounded by palisading crowded basaloid or colu mnar cells or both and rosette-like structures of tumor cells with cen tral fibrillary material. Keratin debris in the background and cystic cavities were prominent components of the metastatic ameloblastoma. Th e basaloid cells showed scant-to-absent cytoplasm, round-ro-oval to te ar-shaped nuclei, rare longitudinal nuclear grooves, single or multipl e nucleoli, and smooth-to-clefted nuclear contours. No features to pre dict malignant behavior were identified (abundant mitotic activity, ne crosis, nuclear pleomorphism). The cytological features of ameloblasto ma appear to be characteristic enough to allow definitive diagnosis. H owever, since the cytology of this tumor is underreported in the liter ature, the unwary observer could easily misdiagnose it, especially at metastatic sites. (C) 1998 Wiley-Liss, Inc.