**5. Solid focal pancreatic lesions**

#### **5.1. Ductal adenocarcinoma**

Ductal adenocarcinomas represent 80–90% of the exocrine pancreatic tumors [23]. They have a poor prognosis, due to both their aggressiveness and the difficult diagnosis in early phases, in which effective treatment can be initiated.

On standard US, ductal adenocarcinoma most frequently appears as a hypoechoic, imprecisely delineated mass which sometimes exceeds the contour of the pancreas (which facilitates detection) (**Figure 5**), but which other times is completely embedded in the pancreatic parenchyma.

In CEUS, ductal adenocarcinoma is only slightly enhancing in the early phase, appearing as hypoenhancing as compared with the adjacent pancreatic parenchyma (**Figure 6**) probably due to the desmoplastic reaction and low mean vascular density [20, 23–25]. This pattern is present in approximately 90% of cases [2, 20, 26]. Moreover, CEUS enables a better visualization and staging of ductal adenocarcinoma by allowing a better delineation as well as assessment of vascular invasion [23, 27–29].

Contrast‐Enhanced Ultrasound for the Assessment of Pancreatic Lesions http://dx.doi.org/10.5772/65066 147

**Figure 5.** Ductal adenocarcinoma in the head of the pancreas, standard US: hypoechoic mass (TU arrows). PA pancreas.

**Figure 6.** Ductal adenocarcinoma in the head of the pancreas, CEUS—arterial phase: hypoenhancing mass (TU—ar‐ rows) as compared to the adjacent pancreatic parenchyma (PA).

Also CEUS enables liver assessment in the late vascular phases, thus allowing visualization of eventual metastases, with a better accuracy than standard US. In the late phase (more than 120 s after the contrast bolus), liver metastases will appear as hypoenhancing focal liver lesions.

#### **5.2. Neuroendocrine tumors**

D'Onofrio et al. evaluated the performance of CEUS to diagnose pseudotumoral CP in a study that included 173 pancreatic masses. CEUS had 88.6% Se, 97.8% Sp, 91.2% PPV, and 96% accuracy for the diagnosis of pseudotumoral CP, while in 94% of cases the inflammatory mass showed moderate enhancement following contrast, similar to the adjacent pancreatic paren‐

A more recent study showed that the blood flow ratio between the superior mesenteric artery and the pancreatic parenchyma evaluated by CEUS correlates with the grade of chronic pancreatitis and concluded that this safe and convenient method may be useful for the early

A special entity is *autoimmune pancreatitis*. It is characterized by a high level of gamma‐ globulins or IgG, presence of auto‐antibodies, mild or absent clinical symptoms. Imaging techniques reveal an enlarged, "sausage‐like" pancreas, with diffuse, irregular thinning of the Wirsung duct (WD), with possible stenosis of the retro‐pancreatic main biliary duct and rarely cysts or calcifications in the pancreatic parenchyma [20]. Autoimmune pancreatitis is some‐ times associated with other autoimmune diseases such as diabetes mellitus, inflammatory

On standard US, in autoimmune pancreatitis the imaging changes are most often diffuse. The pancreas is enlarged, hypoechoic and with a compressed Wirsung duct. Following contrast bolus, the pancreas is moderate or hyperenhancing in the early arterial phase, but also with

Ductal adenocarcinomas represent 80–90% of the exocrine pancreatic tumors [23]. They have a poor prognosis, due to both their aggressiveness and the difficult diagnosis in early phases,

On standard US, ductal adenocarcinoma most frequently appears as a hypoechoic, imprecisely delineated mass which sometimes exceeds the contour of the pancreas (which facilitates detection) (**Figure 5**), but which other times is completely embedded in the pancreatic

In CEUS, ductal adenocarcinoma is only slightly enhancing in the early phase, appearing as hypoenhancing as compared with the adjacent pancreatic parenchyma (**Figure 6**) probably due to the desmoplastic reaction and low mean vascular density [20, 23–25]. This pattern is present in approximately 90% of cases [2, 20, 26]. Moreover, CEUS enables a better visualization and staging of ductal adenocarcinoma by allowing a better delineation as well as assessment

bowel disease, primary biliary cirrhosis, primary sclerosing cholangitis, or lupus.

inhomogeneous enhancement due to lymphocytic infiltration and fibrosis [20].

chyma [20].

diagnose of CP [22].

146 Challenges in Pancreatic Pathology

**5. Solid focal pancreatic lesions**

in which effective treatment can be initiated.

**5.1. Ductal adenocarcinoma**

of vascular invasion [23, 27–29].

parenchyma.

Neuroendocrine tumors may be symptomatic if they are secreting, with specific clinical signs according to the secreted hormone, or asymptomatic if they are nonfunctioning, in this case only nonspecific symptoms are present, secondary to tumoral growth.

Neuroendocrine tumors are hypervascular lesions [30]. On standard US, they have a similar aspect to ductal adenocarcinoma, as hypoechoic masses (**Figure 7**). The differential diagnosis among the two entities is extremely important, for prognosis, as well as for therapeutic strategy, and this is where CEUS can make a difference.

**Figure 7.** Neuroendocrine tumor in the pancreatic head, standard US: hypoechoic mass (TU). Dilated main biliary duct (MBD). GB—gallbladder.

On CEUS, there are different enhancing patterns according to the size and tumor vascularity [23]. Thus, large tumors show an intense enhancement in the early phase, excepting the necrotic areas that are unenhancing, while medium‐sized lesions will also by enhancing in the arterial phase (**Figure 8**) [31]. Both types of lesions are hypoenhancing in the late phase (**Figure 9**). On the other hand, nonfunctioning neuroendocrine tumors can be hypovascular due to their dense hyaline stroma (they also appear as hypointense on CE‐CT) [31, 32].

**Figure 8.** Neuroendocrine tumor in the pancreatic head, CEUS—arterial phase: hyperenhancing mass (arrows). Dilated main biliary duct (MBD). GB—gallbladder.

**Figure 9.** Neuroendocrine tumor in the pancreatic head, CEUS—late phase: hypoenhancing mass (arrows). Dilated main biliary duct (MBD). GB—gallbladder.
