Evaluation of the Liver for Metastatic Disease

Erik K. Paulson, MD1, 1Department of Radiology, Duke University Medical Center, Durham, North Carolina.

Semin Liver Dis. 2001;21(2) 

In This Article

Ultrasound

By ultrasound metastases to the liver usually take on one of the following appearances: (1) hypoechoic mass, (2) mixed echogenicity mass, (3) mass with target appearance, (4) uniformly echogenic mass, (5) cystic mass, or (6) heterogeneous or "coarse" echo texture without focal mass (Fig. 3).[1,67]

Figure 3

Diffuse infiltration of the liver by metastatic renal cell carcinoma. Transverse image of the liver shows a heterogeneous echotexture with diffusely increased echogenicity. This patient proved to have diffuse metastatic renal cell carcinoma.

Most metastatic deposits are solid and mainly hypoechoic relative to the background liver (Fig. 4). Many will exhibit a hypoechoic "halo" (Fig. 5). There is some controversy as to whether the halo is composed of compressed normal liver parenchyma, new proliferating tumor, edema, a rim of hypervascularity around a metastasis, or some combination of these etiologies. Suffice it to say, a solid mass in the liver ringed by a halo is most likely a metastatic deposit.

Figure 4

Ultrasound of the right lobe of the liver reveals a uniformly hypoechoic mass (arrow) that proved to represent lymphoma.

Figure 5

Ultrasound of the left lobe of the liver reveals a mass in the medial segment that has a hypoechoic "halo" (arrows). The presence of a halo generally indicates metastatic disease. The lesion proved to be a metastasis from colon cancer.

In addition to a halo, metastases may take on a "target" or "bull's-eye" appearance due to alternating layers of hyper- and hypoechoic tissue. Like a halo, such patterns are also highly suggestive of malignancy.

A uniformly hyperechoic solid mass is usually a benign hemangioma.[67] However, occasionally metastases will be uniformly hyperechoic and may masquerade as hemangiomas. In this scenario, further imaging or biopsy is indicated. Often, hyperechoic metastases correspond to hypervascular lesions, including metastases from renal cell carcinoma, breast carcinoma, and islet cell tumors (Fig. 6). Hypoechoic masses tend to be hypovascular.

Figure 6

Ultrasound of the liver reveals multiple echogenic masses due to metastatic breast cancer.

Similarly, simple cysts of the liver usually are not confused with cystic metastases, which nearly always contain septations, debris, mural nodules, or thick walls (Fig. 7). Metastases that tend to be cystic include those from sarcomas and squamous cell carcinomas, but any primary tumor may present with cystic metastases, particularly following treatment.

Figure 7

Ultrasound of the liver shows a fluid-filled mass with a peripheral thin rim of viable tumor (arrows). This lesion was a necrotic metastasis from colon cancer. The irregular inner wall (open arrow) and internal echos (curved arrow) are clues that the lesion is not a simple benign cyst.

A promise of color flow and power Doppler imaging was to differentiate metastases from benign tumors or those of hepatocyte origin. Unfortunately, even with the use of US contrast agents, there is considerable overlap in the appearance of metastases and hepatocellular carcinoma (HCC).[21] On a case-by-case basis, clinical and historical factors influence the determination of tumor type more than the sonographic appearance per se.

Calcifications suggest a mucinous adenocarcinoma, which implies a primary site from the colon, pancreas, or ovary (Fig. 8). Thyroid carcinoma metastases may also calcify.

Figure 8

Transabdominal ultrasound shows a mass (arrows) in the right lobe. Note the echogenic central calcifications, which cast an acoustic shadow (open arrow). Note the lesion extends into the inferior vena cava (curved arrow).

One of the strengths of US is to facilitate liver lesion biopsy.[68] With needle tip visualization and the real-time capability afforded by US, the viable nonnecrotic portions of the tumor may be sampled (Fig. 9). Furthermore, portions of the adjacent normal liver may be avoided, which increases the yield of the specimen. With traditional CT guidance, or even with CT fluoroscopy, such precise needle placement is often not possible.

Figure 9

Ultrasound-guided biopsy of necrotic metastasis from colon cancer. Gray-scale image of the liver shows a primarily fluid-filled metastasis from colon cancer. There is a relatively thin rim of viable tumor. With ultrasound, the needle tip (arrow) could be precisely positioned within the rim to biopsy the viable portion of tumor and avoid the adjacent normal hepatocytes or necrotic portions of the lesion. The two solid white lines indicate the anticipated path of the needle using an attachable needle guide. In this case, the needle deflected outside the anticipated path.

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