Objective  This study aims to investigate the importance of nasopharyngeal mucosa typing in the diffusion weighted imaging (DWI) for the diagnosis of nasopharyngeal malignant lesions.

  Methods  Based on the symmetry of nasopharyngeal mucosa and on the comparison between the highest mucosa signal and the spinal cord signal, 91 cases of nasopharyngeal mucosa DWI images were divided into four types, namely, type Ⅰ (low signal and symmetry, 15 cases), type Ⅱ(low signal and asymmetry, five cases), type Ⅲ (high signal and symmetry, 32 cases), and type Ⅳ (high signal and asymmetry, 39 cases). The typing and qualitative results were compared to investigate the relationship between the typing and nasopharyngeal malignant lesions.

  Results  Malignant lesions were not found in type Ⅰ, and only one case of malignant lesions was found in type Ⅱ. No significant differences were observed between types Ⅰand Ⅱ; therefore, these types were merged into "type Ⅰ+Ⅱ." A total of 21 and 37 cases with malignant lesions were found in types I Ⅱ and Ⅳ, respectively. Significant differences were generally found among these types (χ²=46.848, P=0.000), that is, between "type Ⅰ+Ⅱ" and type Ⅲ, "type Ⅰ+Ⅱ" and type Ⅳ, as well as between types Ⅲ and Ⅳ (χ²= 18.533, 46.579, 10.052, P=0.000, 0.000, and 0.002, respectively).

  Conclusion  The DWI images of the nasopharyngeal mucosa showed that suspected malignant lesions should be found in type Ⅲ or Ⅳ. If found to be type Ⅰ or Ⅱ, such lesions should not be clinically considered malignant. Other auxiliary data are needed for diagnosis.