**3.3 Early hepatocellular carcinoma (Early HCC)**

The suggestive appearance of early HCC on 2D ultrasound examination is that of hypoechoic nodule, with distinct pattern, developed on cirrhotic liver. Hypoechoic appearance is characteristic of moderate/poorly differentiated HCC, with low or absent fatty changes. Rarely, HCC may appear isoechoic, consist of a tumor type with a higher degree of differentiation and therefore with slower development. Another common aspect is "bright loop" or "nodule-in-nodule" appearance, hypoechoic nodules in a hyperechoic tumor. (Minami & Kudo, 2010).

Spectral Doppler characteristics of early HCC overlap those of the dysplastic nodule, as they are represented by the presence of portal venous signal type or arterial type with normal RI (well differentiated HCC) or increased RI (moderately or poorly differentiated HCC). The CFM exploration identifies a chaotic vessels pattern.

On CEUS examination, early HCC has an iso- or hypervascular appearance during the arterial phase followed by wash out during portal venous and late phase. There are studies showing that the wash out process is directly correlated with the size and features of neoplastic circulatory bed. Thus, highly differentiated HCC illustrates the phenomenon of late or even very late "wash out" while poorly differentiated HCC has an accelerated wash out at the end of arterial phase (Strobel et al, 2005; von Herbay et al, 2009; Jang et al, 2009). It is therefore mandatory to analyze all these three phases of CEUS examination for a proper characterization of liver nodules. Tumor wash out at the end of the arterial phase allows the HCC diagnosis with a predictability of 89.5%. Some authors consider that early pronounced contrast enhancement of a nodule within 1-2 cm developed on a cirrhotic liver is sufficient for HCC diagnosis (Jang et al, 2009). These results prove that for a correct characterization of the lesions it is necessary to extend the examination time to 5 minutes or even longer (von Herbay et al, 2009).

Fig. 11. Early hepatocellular carcinoma (2D, CFM). The 2D examination reveals a solid, hypoechoic nodule in IVth liver segment, without encapsulation. CFM shows a central vessel with ramifications to the periphery. The underlying liver is cirrhotic.

Fig. 12. Early hepatocellular carcinoma (2D, CFM). "Nodule in nodule" image: small hypoechoic early HCC inside monitored dysplastic nodule.
