a Differentiated variant of nonkeratinizing nasopharyngeal carcinoma showing a cluster of cells that have a moderate amount of cytoplasm that is keratinized in some cells, large nuclei with vesicular chromatin and prominent nucleoli. Papanicolaou stain, ×600. b Undifferentiated variant of nonkeratinizing nasopharyngeal carcinoma showing bare tumor cell nuclei in a lymphoid background; these nuclei are large, round to oval and have prominent nucleoli. Diff-Quik stain, ×400.