What exactly are liver lesions?

Depends: Liver lesions can be used to describe an area of cancer (from liver or from other areas) but can also be used to describe hemangiomas (collection of blood vessels) or cysts. Sometimes when the "lesions" are so small in can be hard to determine what it is exactly.

Masses: Liver lesion is another way to describe a mass in the liver. There are many different types of masses and they can be benign or malignant. Cyst can sometimes be referred to as lesions. Most of the time a mix of differnent types of x-ray tests and possibly a biopsy can figure out what it is.

Irregularities: Liver lesions implies that there are areas where the homogeneity of the liver is not complete. Most often and when they are detected incidentally, they represent one of many noncancerous abnormalities that can be seen in the liver. When discovered during an evaluation for symptoms, labwork irregularites, or in an older age group, cancer enters the equation.