Reversal of Pale-to-dark Nasopharyngeal Follicle Ratio on Narrow-band Imaging

Normal nasopharyngeal mucosa contains varying amounts of lymphoid tissue, which in adults may be minimal or absent. Nasopharyngeal mucosa with minimal lymphoid tissue has a regular follicular pattern on narrow-band imaging; pale follicles have thin, dark borders and the ratio of the pale follicle to the dark border (pale-to-dark ratio) is roughly 90%. In some patients undergoing routine nasopharyngeal endoscopy, the pale-to-dark ratio is reversed on narrow-band imaging, with dark centres surrounded by pale borders and a pale-to-dark ratio of roughly 50%. These dark follicles may represent abnormal capillary loops, as they have the same appearance as microvascular changes seen on narrow-band imaging of the oesophageal mucosa which indicate dysplasia or malignancy. While this observed change in the follicular pattern may be an early event in the evolution of nasopharyngeal carcinoma, the significance of this finding remains to be confirmed by a larger-scale study.