Introduction
This topic covers focal liver lesions: space-occupying lesions that are visible as a discrete mass on imaging. It covers the main benign and malignant primary liver tumours and liver metastases, with emphasis on how imaging characterises them, which lesions can be diagnosed without biopsy, and how they are differentiated from each other. Imaging technique for the liver as a whole is covered in the previous topic and is only referred to here.
General approach to a focal liver lesion
Most focal liver lesions are found incidentally on ultrasound or CT. The first questions are whether the lesion is benign or malignant, whether the liver is cirrhotic, and whether the patient has a known extrahepatic primary cancer. The answers determine the differential diagnosis and the need for further imaging or biopsy.
- Key features to describe: size, number, margins, internal architecture, and behaviour after contrast.
- Multiphasic contrast CT or MRI is the standard for characterisation: arterial, portal venous and delayed phases.
- Hepatobiliary-specific MRI contrast (gadoxetate) adds a hepatobiliary phase, showing whether lesions contain functioning hepatocytes.
- Contrast-enhanced ultrasound (CEUS) is an accurate alternative for characterising lesions and for follow-up.