A liver tumour as an incidental finding: differential diagnosis and treatment.

BACKGROUND: A liver tumour is occasionally found by coincidence during upper abdominal imaging. The diagnostic and therapeutic strategy for incidental liver tumours is discussed.
METHODS: Review of the literature.
RESULTS: When a liver tumour is found by coincidence, the questions to be answered are whether a definite diagnosis can be reached by imaging alone, and whether treatment is indicated. To answer the first question we have to know the characteristics of the various liver tumours with different imaging techniques, and the added value of more invasive diagnostic procedures. For an answer to the second question, information on the natural course of the specific tumour and on the risks and benefit of treatment is required. Of course, the a priori chance of certain diagnoses depends on the presence or absence of risk factors. Using simple imaging techniques, liver lesions can be categorized as single or multiple and as cystic or solid. Cystic lesions are usually benign, either congenital or parasitic. Solid lesions can be benign or malignant. The most common benign lesions are haemangioma, focal nodular hyperplasia and hepatocellular adenoma. Malignant tumours arising in the normal liver can be primary, in the form of hepatocellular carcinoma, or secondary, resulting from dissemination of a primary tumour outside the liver. All these tumour types can present with typical features in various imaging studies. A definite diagnosis based on imaging alone, however, is not always possible. On the other hand, even histological examination of biopsy samples sometimes does not differentiate between benign and malignant tumours. In the case of an asymptomatic liver tumour the main indication for treatment is proven or suspected malignancy. Large adenomas form a notable exception, these should be removed if they are over 5 cm in diameter or when they grow during follow-up, especially during pregnancy. Therapy will usually consist of liver resection, either partial or, when this is not possible, complete resection followed by liver transplantation. An important caveat is that a surgical procedure without morbidity and mortality does not exist. For symptomatic benign liver tumours the options are the same, but there may be equally effective and less risky alternatives in specific cases, such as embolization for focal nodular hyperplasia and irradiation for haemangioma.
CONCLUSION: The diagnostic and therapeutic approach to incidental liver tumours depends on several factors, including size, aspect and number of the tumours, the clinical background, the a priori chance of a certain type of tumour and especially the risk of malignancy.