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HEPATIC METASTASIS

The most common liver metastases originate from -in decreasing order- lung, colon, pancreas, breast, and stomach carcinomas. The highest prevalence of metastasis occurs with gallbladder, pancreas, colon, and breast carcinoma; the lowest with prostate carcinoma.

 Metastatic disease is multifocal in approximately 90 percent of patients (Picture1). Occasionally metastatic disease may be solitary or confined to one segment or lobe, in which case surgical resection of part of the liver is possible. Uncommonly, liver metastases may present as a diffuse process throughout the liver, and differentiation from normal or other diffuse liver diseases may be difficult.


Picture1. Multiple, small metastases.

The ultrasound pattern of liver metastases is quite varied, and there is no consistent relation between ultrasound patterns and type of tumor that allows one to specify the primary malignancy [1]. The various ultrasound patterns include multiple hypoechoic (Picture2), hyperechoic, and isoechoic foci. Hypoechoic halos are common. Target or bull's eye patterns with varying rings of hypo-and hyperechogenenicity are common. Hypoechoic rims may comprise liver parenchyma or tumor. An ill-defined infiltrative lesion with focal nodularity is another fairly frequent patern. Metastases that simulate simple cysts or classic appearing hemangiomas are uncommon. An anechoic foci indicates the necrotic or hemorrhagic components. Predominantly fluid-filled, presumably necrotic metastases occur most frequently with squamous cell carcinoma, sarcomas, and ovarian and testicular carcinoma. Some metastases, especially the ones arising from mucinous adenocarcinoma may calcify. 


Picture2. Hypoechoic metastases.

Although sonographic appearance is a poor predictor of the primary tumor, certain patterns are suggestive [2]. Large to moderate sized hyperechoic metastases should suggest the possibility of a colonic primary. Lesions with fluid-fluid levels (representing intralesional necrosis and hemorrhage) are often found with metastatic leiomyosarcoma.

Metastasis and hepatocellular carcinoma may be impossible to distinguish clinically or sonographically. When the diagnosis is unclear clinically or when a definitive diagnosis is required, sonographically guided biopsy should be performed. Invasion of the portal or hepatic veins suggest hepatocellular carcinoma, rather than metastasis.

In follow-up assessment during and after therapy, one often sees a change in the ultrasound texture of the metastases, but the size and number of metastases provide a more reliable indicator of response to therapy. For sequential ultrasound scans in metastatic disease, one must scan the liver in a thorough and consistent way in transverse and sagittal/coronal planes to make comparisons with previous exams [2].

REFERENCES:
[1]Abdominal Ultrasound. E.E.Sauerbrei, K.T.Nguyen, R.L.Nolan. 1992.
2]Sonography of the Abdomen. R.B.Jeffrey, P.W.Rolls. 1995


 

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