Ultrasound diagnosis of metastatic liver tumors

The incidence of liver metastatic malignant tumors is high, and its incidence is related to the type and clinical stage of the primary tumor. Most tumors metastasize to the liver through the portal vein and hepatic artery, but stomach, pancreas, ovary and uterine tumors also often metastasize through the lymphatic channels. Tumors of some adjacent organs such as gallbladder, kidney, stomach, colon, etc. can directly invade the liver. Ultrasound diagnosis of metastatic liver tumors has great development.

Metastatic liver tumors have no obvious symptoms in the early stages. When clinical symptoms appear, they are similar to those of primary liver cancer. In a small number of patients, metastatic lesions in the liver are first discovered, while the primary tumor is very small and difficult to detect.

Ultrasound diagnosis: 2D ultrasound

(1) Direct signs: Metastatic liver tumors generally present as multiple round or quasi-round masses in the liver with clear boundaries. The echoes inside the masses vary greatly depending on the tumor source, component structure, and degree of necrosis, and can be divided into high echo, low echo, equal echo, no echo, and mixed echo types.

① High echo type: the most common. Primary tumors of the digestive system (especially colon cancer), larger metastatic tumors, and metastatic tumors after radiotherapy or chemotherapy are often high echo type. The echo of high echo nodules is often higher than that of hemangiomas, the internal echo is uneven, and an acoustic halo can be seen around it. Typical liver metastases show "bull's eye sign" or "target ring sign", that is, the cancer is high echo inside, and a thick low echo halo with a width of 0.5 to 1CM can be seen around it. Sometimes low or no echo area can be seen in the center of the high echo. The mass generally has no lateral acoustic shadow, and the posterior echo is not significantly enhanced.

② Hypoechoic type: Common in liver metastases of breast cancer, small cell lung cancer, pancreatic cancer, leiomyosarcoma, melanoma, and some lymphoid tumors. In addition, liver metastases occurring on the basis of fatty liver also often show a hypoechoic type. This type of mass is often small, with low internal echoes, clear boundaries, and may also have acoustic halos.

③ Iso-echoic type: The echo of the mass is similar to that of normal liver parenchyma, which is easy to be missed. However, there may be a weak echo halo around the mass, and nearby blood vessels may be squeezed, bypassed or interrupted, so careful observation is required.

④Anechoic type: less common. More common in liver metastasis of lymphoma, melanoma or cystadenocarcinoma. The mass has very low echo, similar to liver cyst, with clear boundaries, but no thin and bright cyst wall.

⑤ Mixed echo type: It can be seen in liver metastases with secretory function, such as mucinous adenocarcinoma originating from the gastrointestinal tract, endocrine tumors of the pancreas, adrenal tumors, etc. The mass is large in size, with obviously uneven echoes inside, and may have liquefaction necrosis or calcification spots.

In addition to the above-mentioned manifestations of multiple nodules in the liver, a few metastatic liver tumors also present as single masses, diffuse infiltration, and direct infiltration in the liver. Diffuse infiltration metastatic tumors have no obvious masses, but only show thickening and disordered liver echoes with uneven distribution. The sonographic manifestations are similar to other diffuse liver lesions such as cirrhosis, and are easily missed.

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