Immunohistochemistry for topoIIα in salivary gland tumors. A: Pleomorphic adenoma: few positive nuclear expressions in tumor cells (×100). B: Warthin's tumor: abundant positive expression in lymphoid cells of germinal centers, not in epithelial tumor cells (×100). C: Adenoid cystic carcinoma (Grade 1): low expression in low-grade tubular components (×100). D: Adenoid cystic carcinoma (Grade 3): high nuclear expression in high-grade solid areas (×100). E: Salivary duct carcinoma: many positive cells in foci with typical comedonecrosis (×100). F: Salivary duct carcinoma: strong and diffuse expression observed in the invasive micropapillary variant (×200).