Table 1.

Elements of differential diagnosis between HPV + and HPV- oropharyngeal cancer across different imaging techniques

Imaging technique	HPV+	HPV-
Ultrasound
Primary lesion	-	-
Metastatic lymph nodes	Size > 8 mm (9 mm subdigastric IIa) Round shape
Metastatic lymph nodes	Hypoechoic cystic necrosis	Hyperechoic spots (coagulation necrosis)- rare Intranodal calcification
CT
Primary lesion	Smaller Exophytic growth Well defined borders	Bigger Ill-defined borders Grows by invading submucosa and adjacent muscle tissue Necrosis Ulceration
Metastatic lymph nodes	Cystic necrosis Well-defined borders Clustering	Extra-nodal extension Ill-defined borders Matting
PET-CT
	Higher SUVmax	Lower SUVmax
Conventional MRI
Primary lesion	Same elements as CT but better overall definition
Metastatic lymph node	Same elements as CT but better overall definition
DWI
Primary lesion	Lower ADC and D_t; Leptokurtic Right skewed ADC histogram	Higher ADC and D_t; Symmetric Normally distributed ADC histogram
Metastatic lymph node	Lower ADC and D_t; Leptokurtic Right skewed ADC histogram
IVIM	No significant difference in D*, skewness, kurtosis
DKI	No significant difference in D*, skewness, kurtosis
DCE-MRI
Primary lesion	Inconstant lower values of k_trans	-
Metastatic lymph node	Inconstant lower values of k_trans	-