Lectures

Contrast-Enhanced UltraSonography (CEUS) of pancreatic tumors

CYSTIC TUMORS

Serous Cystic Tumor

Serous cystadenoma usually has a benign nature (Compagno and Oertel 1978 a). The typical variety is the microcystic, macroscopically characterized by multiple small cysts (<2cm) separated by thin septa (Procacci et al 2001a, Procacci et al. 1999a). The margins are well-defined and a central scar may be present (Procacci et al. 1999a). At CEUS intralesional septa enhancement improves identification of the microcystic features of the lesion. The less common oligocystic or macrocystic types of serous cystadenoma present features undistinguishable from those of the other macrocystic tumors of the pancreas (Carbognin et al. 2003; Procacci et al. 1997).

Mucinous Cystic and Intraductal Papillary-Mucinous Tumors

Mucinous cystadenoma (MCA) is a rare primitive pancreatic tumor. However, it is the most common cystic pancreatic tumor (Hammond et al. 2002). MCA is considered a pre-malignant lesion (Compagno and Oertel 1978 b, Procacci et al. 1999a, Cohen-Scali et al. 2003). It follows that a radiological characterization of MCA from other cystic pancreatic lesions is important for a correct therapeutic approach. MCA presents as a cystic round mass, multilocular or less often unilocular, with variable size (Buetow et al. 1998; Fugazzola et al. 1991). The multilocular kind is typical, though not pathognomonic (Sperti et al. 1993). The unilocular type is less common and less specific and enters into differential diagnosis with the other cystic lesions of the pancreas (Demos et al. 2002), especially pseudocysts (Buetow et al. 1998, Sperti et al. 1993, Scott et al. 2000, Procacci et al. 1999a, Sachs et al. 1989, Warshaw et al. 1987, Kuba et al. 1998, de Lima et al. 1999, Fugazzola et al. 1993, Hammond et al. 2002).

MCA may present calcifications on the wall or the septa (Procacci et al. 2001b), parietal nodules and papillary vegetations (Fugazzola et al. 1991). The cystic content of the lesion may be inhomogeneous for the presence of mucin or intralesional hemorrhage. At US MCA presents as a lesion with cystic areas, separated by septa, with a finely corpuscular content for the presence of mucin. Using tissue harmonic it is possible to better evaluate the walls, septa, nodules and the papillary vegetations in the wall, which appear to be better evaluable at US than at single slice spiral CT (Hammond et al. 2002). The content of the MCA, however, if very corpuscular, may impair identification of parietal nodules, which is fundamental for a radiological diagnosis. CEUS may significantly add to the ultrasonographic identification of MCA parietal nodules and septa. In particular, contrast-enhanced ultrasonography with second generation contrast medium, thanks to the dynamic observation of the contrast-enhanced phases, allows a demonstration of the enhancement of nodules and intracystic septa, due to their tumoral nature, which become hyperechoic.Cystic tumor: vascularized septa and/or nodules

CEUS examination moreover improves ultrasonographic differential diagnosis between MCA and pseudocyst thanks to the accurate identification and study of the vascularization of inclusions in cystic masses of the pancreas (D’Onofrio at al. 2007).
Intraductal Papillary-Mucinous Tumors (IPMT) are considered a rare lesion, but recently have been reported with increasing frequency (Procacci et al. 1996; Procacci et al. 1999b; Procacci et al. 2001c; Procacci et al. 2003). IPMT is macroscopically characterized by intraductal origin and growth (Zamboni et al. 2003) which may happen with the production of dense mucin that fills the Wirsung duct (ductectatic mucin-hypersecreting variant) or with endoluminal papillary proliferation (papillary-villous variant). At ultrasonography dilation of the main pancreatic duct is usually demonstrated. Ultrasonographic demonstration of the lesion however depends on its size. Intraductal Papillary-Mucinous Tumors of adequate dimensions appear at US as highly inhomogeneous masses, upstream of the Wirsung dilation, of difficult US characterization. CEUS examination of the IPMT may allow identification of intraductal papillary tumoral vegetations (Itoh T et al. 2005). However, a final diagnosis of IPMT by demonstrating the communication between the tumor and the pancreatic duct is difficult with US (Procacci et al. 2003).