Differential Diagnosis

The approach to characterizing a focal liver lesion seen on CT begins with the determination of its density. If the lesion is of near water density, homogenous in character and has sharp margins, then a cyst should be considered and can be confirmed with an equilibrium phase CT, US or MRI (T2 bright and non-enhancing post gadolinium).

If the lesion has some enhancement, then the next analysis requires a determination of whether the enhancement is peripheral and nodular, with the density of the lesions appearing similar to density of blood vessels. In this case, a hemangioma may be diagnosed with confidence. On the other hand, thick irregular, heterogeneous enhancement suggests a malignant mass.

Arterially enhancing lesions include FNH, hepatocel-lular adenoma, HCC and metastases from carcinoid, melanoma, renal cell carcinoma, breast, sarcoma and islet cell tumor. In general, HCC is considered when there is a setting of cirrhosis, while FNH is considered in young women and hepatic adenoma in patients on oral contraceptives, anabolic steroids or with history of glycogen storage disease.

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