The primary objective of the study is to determine the accuracy of CEUS in characterizing (as benign or malignant) focal liver lesions for which CT, MRI and/or PET have not been conclusive.

The study conducted will be a non-profit, observational, non-pharmacological, cross-sectional, but also partly cohort, retrospective and prospective study. The study is cross-sectional in nature, but will require 6 months of follow-up to evaluate the gold standard reference outcome in patients diagnosed with a benign pathology that does not require further investigations, and in patients with suspected malignant lesion for which histological diagnosis has not been performed on biopsy.

Inclusion Criteria:

• Age ≥18 years.
• CEUS performed performed in the last 6 months a CT, MRI and/or PET not decisive in characterizing a liver lesion.
• Obtaining informed consent.

Exclusion Criteria:

• Technical impossibility to perform the ultrasound evaluation.
• Documented allergy to the ultrasound contrast medium.

All patients who have previously resulted positive to CT, MRI and/or PET scans for liver lesions but with no information on the nature of the lesion and that will undero CEUS for further characterization of the lesion(s) will be consecutively enrolled.