Malignant intrahepatic lesions:

14.1.4.2.1. Metastasis

The most common malignant intrahepatic lesions are the metastases of various origin. In the oncologic praxis especially in case of a patient with known colorectal, neuroendocrin or breast cancers, focused ultrasound examination of the liver has a special importance during the checkups. US appearence and detectibility of the liver metastases can be very variable depending on the primary tumor. Sensitivity ranges between 53% and 84% according to various large studies. Characteristically hypoechoic liver metastases originate usually from:

Breast cancer (Figure 23), pancreatic cancer, testicular cancer, ovarial cancer, malignant lymphoma, carcinoid, gastrointestinal adenocarcinoma.

Figure 23: Metastases of breast cancer in the liver, contrast enhanced CT

187 Characteristically hyperechoic liver metastases appear in case of the following primary

tumors:

Colorectal adenocarcinoma, malignant melanoma, small cell bronchial carcinoma, teratoid carcinoma, gastric adenocarcinoma, certain part of breast cancers.

- Diffuse, infiltrative liver metastases can be observed:

In case of anaplastic carcinoma and purely differenciated tumors.

Besides these forms, metastases with mixed echostructure (containing both hyperechoic and hypoechoic areas) and cystic metastases with necrotic content can occur relatively often (Figure 24).

Figure 24: Metastases of a GIST tumour, US

The liver metastases of colorectal origin are usually characterised by a bit inhomogeneous hyperechoic structure sorrounded by a hypoechoic rim. (Figure 25)

Figure 25: Liver metastasis of rectal cancer, US

In the central area of bigger (4-6 cm in diameter) metastases necrosis can also develop as so called „target‖ form (or commonly called as bull’s eye sign).

In the oncological practise, the most often performed imaging modality is nowadays the CT which is appropriate for both searching of liver metastases and the follow-up of the treatment efficacy in case of known liver metastasis. The decreased or increased vascularisation of the metastases can be well documented by appropriately performed three-phase multidetector CT in case of the liver, even from the size of 4-5 mm in most of the cases.

Far before the era of multidetector CT, CT arterioportography (CTAP) was performed in special cases. The sensitivity and specificity of CTAP in the detection of liver metastases was far better as the conventional spiral CT. In the course of CTAP, a selective catheter was

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placed from the arterial side into the superior mesenteric artery or the splenic artery.

Following 35-40 sec delay after 80-90 ml contrast administration (by injector) the spiral CT scan was performed in the portal phase.

The MRI is very sensitive to the detection of metastases, their surprising multiplicity can be detected by MRI even in case of negative CT and US examinations as well.

MRI signal intensity is dependent on their water content.

- T1-weighted signal intensity is usually lower

- T2-weighted signal intensity is higher compared to the liver parenchyma.

The image may be dotted with hemorrhages (according to their age) and calcifications (according to their extent). There are some tumors whose metastases bleed frequently (melanoma). Often, certain metastases can be recognized only after contrast administration.

14.1.4.2.2. Hepatocellular Carcinoma (HCC)

2500-3000 new HCC cases are recognised in the Hungarian population yearly. Its prevalence is more frequent in the Far Eastern population (China, Japan, Korea) and in the South

European countries (Italy, Greece, Spain).

HCC is the most frequent primary liver tumor originating from the hepatocytes. Chronic viral hepatitis, liver cirrhosis (alcohol or other toxic origin) and other carcinogenous materials (drugs, aphlatoxin) can play a role.

The blood supply of HCC is received mainly from the hepatic artery, explaining the US, CT and MR image features.

Their US apperarences include mostly an inhomogeneous, hyperechoic or hypoechoic lesion, which is arterially hypervascularised, and several arterioportal shunts may develop. The demonstration of shunt related portal vein flow disturbance by doppler US has a prominent importance. The adjudication of the cirrhosis related HCC by ultrasound is often a particularly difficult task.

HCC appears mostly as low density on the native CT scan, with inhomogeneous structure and a sorrounding with a slightly increased density bearing capsule can be also detected. The completion of the three-phase CT scan (arterial, venous, late) is especially important in case of a suspicion of HCC. The appearance of the inhomogeneous lesion in the arterial phase, including sometimes non contrast enhancing necrotic areas inside, bears with a diagnostic value. The capsule can be detected best in the venous phase.

The primary hepatic cancers respect usually the liver borders. At the time of death, mainly regional lymph node metastasis is observed in almost half of the cases. Besides that, lung, bone and suprarenal metastasis can occur.

MRI findings:

- Lower signal intensity can be usually but not necessarily observed compared to the liver parenchyma on the T1-weighted images. The possible capsule appears as even lower ring-like signal intensity.

- On T2-weighted images, the hepatocellular carcinoma has a high signal intensity according to the necroses, but in case of no necrosis the tumor can be isointense!

Recent haemorrhages, hemosiderin, fat deposition influence the signal intensity characteristically.

The differenciation of the foci and the nodular regenerative hyperplasia is very difficult.

Concerning the HCC, the knowledge of history is very important for the decision and usually the oncoteams consider the performance of an imaging modality guided biopsy basically important for the further therapeutic decisions (because of the hystological validation rather core biopsy should be performed! (Figure 26, 27, 28).

189 Figure 26: HCC, verified with FNAB, US

Figure 27: HCC, TAE, agniography

Figure 28: HCC, native CT after TAE 14.1.4.2.3. Less frequent primary liver tumors:

 Rhabdomyosarcoma

 Liposarcoma

 Hepatoblastoma

 Fibrolamellar HCC

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Other pathological liver lesions: