Fig. 1

Hematoxylin–eosin (HE) staining of nasopharyngeal tissue sections and brushing smears (40×). a Nasopharyngeal tissue from a nasopharyngitis patient shows inflammatory nasopharyngeal epithelium infiltrated with plenty of lymphocytes. b Poorly differentiated nasopharyngeal carcinoma (NPC) tissue shows tumor nests surrounded with lymphocytes. c Brushing smear sample from a healthy participant shows normal nasopharyngeal mucosa, consisting of columnar cells, squamous cells, and lymphoid cells. d Brushing smear sample from a NPC patient shows typical NPC cells with large nuclei, a high nuclear/cytoplasmic ratio, and prominent nucleoli. Arrows indicate tumor cells