The vast array of liver lesions encompasses both benign and malignant in nature as well as primary and metastatic tumors. The widespread use of imaging studies within the last two decades has allowed these lesions to be diagnosed earlier or as an incidental finding. This compendium is focused on providing the most practical and up-to-date information on this very broad topic. Throughout this chapter, we cover the “high-yield” features of the most common liver lesions in patients with both normal and underlying chronic liver disease. The ultimate goal is for this to serve as a guide for emergency and primary care providers to make their most informed decision regarding the workup and further management of these patients and whether or not they require surgical consultation. Given the practical approach of this manual, we will classify liver lesions in both benign and malignant, outlining their most relevant characteristics and providing specific recommendations regarding the need for surgical consultation. Tables 44.1 and 44.2 summarize the key steps in the management of both benign and malignant lesions, along with the appropriate referral physician for each case. Small liver lesions that are seen at the time of a scan for other reasons can be difficult to evaluate. In general, one must ensure that these are solid versus cystic as most cystic lesions of the liver are benign. MRI or ultrasound is very effective in delineating cystic lesions—hypoechoic in the former, and T2-bright in the latter case. In general, solid lesions will need to be watched and cannot be ignored if they are too small to characterize by imaging or target for biopsy. In this case, repeat imaging to demonstrate the lack of growth will be the main premise.