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Fig. 6. Liver metastases from breast cancer. a Contrast enhanced Spiral CT. b SPIO-enhanced T2-weighted MR image, note the improved detection and delineation of the metastases (arrow)

Fig. 6. Liver metastases from breast cancer. a Contrast enhanced Spiral CT. b SPIO-enhanced T2-weighted MR image, note the improved detection and delineation of the metastases (arrow)

Hepatic Abscesses

Abscess appearances can vary depending on etiology (peribiliary abscesses tend to be small and scattered adjacent to the biliary tree; portal distribution of infection from appendicitis or diverticulitis tends to lead to larger cystic lesions).

Table 1. MR features

Tl-weighted hyperintense lesions

Probable cause of hypertensity

Melanoma metastases Colonic adenocarcinoma Ovarian adenocarcinoma Multiple myeloma Pancreatic mucinous cystic tumor

Melanin, extracellular methemoglobin

Hemorrhage or coagulative necrosis

Protein

Protein

Protein

US reveals a cystic lesion with internal echoes. On CT, hepatic abscess appears as a hypodense lesion with a capsule that may show enhancement. 'Cluster sign' may be noted as focal clusters of lesions when multiple abscesses are present [23]. The CT appearance of hepatic abscess is non-specific and can be mimicked by cystic or necrot-ic metastases. Though present in only a small minority of cases, presence of central gas is highly specific for abscess. On MRI, hepatic abscesses are hypointense relative to liver parenchyma on Tl-weighted images and markedly hyperintense on T2-weighted images, often surrounded by a local area of slight T2 hyperintensity representing perilesional edema.

The CT appearance of amebic liver abscess is nonspecific. It usually appears as a solitary, hypodense lesion with an enhancing wall that may be smooth or nodular, often associated with an incomplete rim of edema. With MRI, the lesions are hypointense on Tl-weighted images and heterogeneously hyperintense on T2-weighted images [24].

Table 2. Classification of common hepatic neoplasms

Cell Type

Benign

Malignant

Cholangiocellular

Hepatic cysts Biliary cystadenoma Bile duct adenoma

Biliary cystadenocar-cinoma

Cholangiocarcinoma

Hepatocellular

Hepatocellular adenoma Focal nodular hyperplasia Nodular regenerative hyperplasia Adenomatous hyper-plasia

Hepatocellular carcinoma

Fibrolamellar hepato-cellular carcinoma

Mesenchymal

Mesenchymal hamartoma

Hemangioma

Infantile hemangio-

endothelioma

Lymphangioma

Lipoma, angiomyo-

lipoma

Leiomyoma

Fibroma

Angiosarcoma Connective tissue sarcoma Undifferentiated embryonal sarcoma

Miscellaneous

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