Fig. 4

a The smooth nasopharyngeal mucosa was found under the WL mode, which had a ruddy color. No obvious tumor profile was found. b Within the range guided by the arrow in the WL view field under the NBI mode, a disordered distribution and the circuitous superficial vessels of the mucosa were found. The walking shape was parallel to the mucosa. c Right nasopharyngeal superficial vessels under the NBI mode were observed, with clear texture. No typical and special-shaped vessels were revealed. The nasopharyngeal tissue was submitted for pathological examination on the position guided by the arrow, with a definite diagnosis of undifferentiated and non-keratinizing carcinoma