Proposed MR imaging criteria for primary NPC detection
| Grade | Condition | Appearance |
|---|---|---|
| 1 | Normal | Thin mucosa ≤3 mm; adenoid absent, vestigial or composed almost entirely of cysts |
| 2 | Probably benign | Diffusely thickened >3-mm symmetric mucosa either homogeneously enhancing (benign hyperplasia type 1) or with greater contrast enhancement in the deep layer (mucosal white line) compared with the superficial layer (benign hyperplasia type 2); adenoid with intact contrast-enhancing septa (benign hyperplasia type 2) |
| 3 | Indeterminate | Diffusely thickened >3-mm mucosa asymmetric in thickness; adenoid asymmetric in thickness |
| 4 | Suspicious | 1) Diffusely thickened >3-mm mucosa asymmetric in signal intensity; adenoid asymmetric in signal intensity |
| 2) Diffusely thickened mucosa >3 mm with focal loss of the mucosal white line; absence/distortion of the thin contrast-enhancing adenoidal septa (not attributed to cysts) | ||
| 3) Focal mass confined within the nasopharynx | ||
| 5 | Probably malignant | Superficial extension to the nasal cavity/oropharynx or deep extension to the sites bordering the nasopharynx |