RESUMEN
<p><b>OBJECTIVE</b>To study the cytologic features of pancreatobiliary tumors in endoscopic retrograde cholangiopancreatography (ERCP)-guided brushing preparations and to evaluate the usefulness of cytology in the diagnosis of pancreatobiliary malignancy.</p><p><b>METHODS</b>A retrospective analysis of 212 cases of ERCP-guided brush cytology smears performed during the period from January, 2004 to December, 2006. The cytologic diagnosis was confirmed either by the histologic diagnosis or the strict clinical criteria.</p><p><b>RESULTS</b>Two of the cases studied were unsatisfactory for diagnosis, with no epithelial cells identified. One hundred and thirty-seven smears were diagnosed as "negative", 45 of which subsequently confirmed to be malignant (negative predictive value = 60.2%). Six of the 11 cases with "low-grade atypia" were proven to be malignant (positive predictive value = 54.5%), as compared to 19 of 23 cases of "high-grade atypia" (positive predictive value = 86.4%). All of the 41 cases with cytologic diagnosis of "malignancy" were confirmed to be malignant (positive predictive value = 100%). The cytologic features of malignancy in ERCP-guided brushing preparations included overlapping nuclei, anisonucleosis, coarse chromatin pattern, poor cellular cohesion, tumor diathesis, prominent nucleoli and atypical mitotic figures.</p><p><b>CONCLUSIONS</b>The accuracy of ERCP-guided brush cytology relies on good specimen preparation and application of morphologic criteria. Grading of cytologic atypia is of clinical significance. A "negative" or "low-grade atypia" cytologic diagnosis requires further diagnostic workup to rule out the possibility of underlying malignancy, while a "high-grade atypia" or "malignant" diagnosis is relatively specific in guiding subsequent management of suspected pancreatobiliary malignancy.</p>