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Introduction

Pancreatic ductal adenocarcinoma (PDAC) represents 80-95% of exocrine pancreatic tumors, being slightly more common in men; the average patient age is between 50 and 70 years old. Risk factors such as smoking, alcohol, diabetes and pancreatitis may be present. The tumor can be located into the pancreatic head (60-70 % of cases), in the body (20-25% of cases), or in the tail of the pancreas (10% of cases). Only 14% of patients have tumors strictly localized into the pancreatic tissue at the first imaging diagnostic. Local extension of the PDAC can be posterior (in 96% of cases), anterior (in 30% of cases), into the hepatic hilum (in 15% of cases), in the splenic region (in 13% of cases), or in adjacent organs: duodenum, stomach, transverse colon, adrenal organs, spleen and renal mesentery. Pancreatic ductal adenocarcinoma metastasizes to the liver (30-36%), lymph nodes (15-28%), peritoneum (7-10%), lung, pleura and bone structures^(1-7).

Symptoms

The clinical presentation is dominated by weight loss, fatigue, anorexia, obstructive jaundice (75% of cases) and pain⁽¹⁾.

Imaging methods

The reference – and, at the same time, the preferred imaging technique – for the pretherapeutic assessment of PDAC is represented by the native and postcontrast multislice CT (MSCT) examination of the abdomen with thin slice thickness (less than 3 mm) in late arterial (pancreatic) and venous (portal) phases^(1-7), followed by a late venous phase CT evaluation of the thorax and pelvis region.

MSCT findings

Pancreatic ductal adenocarcinoma may correspond to a focal pancreatic mass (95% of cases), a diffuse enlargement of the pancreas (4% of cases), or a normal appearance but with the individualization of the positive double duct sign materialized by dilatation of the common bile duct (CBD) and the main pancreatic duct (Wirsung duct; 1% of cases); in most cases, the tumo­ral pancreatic nodule is hypodense and hypovascular; pancreatic head tumors may associate dilatation of the CBD and intrahepatic bile ducts (IHBD), dilatation of the Wirsung duct, hypotrophy or atrophy of the body and tail of the pancreas. In 2% of PDAC cases, calcifications are present (2%) and in 11% pseudocysts are present. It is of major importance to be specified in the CT report by analyzing post-contrast source images, multiplanar reconstructions (in coronal oblique and sagittal planes) and MIP angiographic reconstructions of the arterial involvement (superior mesenteric artery – SMA; celiac trunk – CTk; common hepatic artery – CHA) and also of the venous structures (superior mesenteric vein – SMV; portal vein – PV; splenic vein) in order to establish the criteria for resectability, borderline or locally advanced pancreatic tumor^(1-8). If the pancreatic tumor presents a cleavage plane with adjacent vascular structures, it is considered resectable (Figure 1).

The invasion of the duodenum, stomach, transverse colon or transverse mesocolon is not a contraindication for surgical intervention. If the PDAC is only in contact or circumscribes less than or equal to 50% of the lumen of the SMA, or it is in limited contact with the CTk or CHA, the tumor is considered borderline⁽⁷⁾. Tumor abutment is defined as circumferential tumor contact ≤180° with the vessel, and tumor encasement refers to >180° tumor contact with the vessel⁽⁷⁾. Teardrop sign is a shape modification of the affected vein on axial CT images due to tumor encasement or desmoplastic reaction, being highly associated with venous invasion⁽⁷⁾. Related to the SMV and PV, pancreatic ductal adenocarcinoma is considered borderline when it comes into contact over a small length that allows reconstruction, with or without contour deformation, with or without venous thrombosis (Figure 2).

When the tumoral process circumscribes more than 50% of the SMA, CTk, CHA with the involvement of the proper hepatic artery, or when it extends towards the median retroperitoneum with the involvement of the abdominal aorta, the tumor is inoperable^(2,3). If the tumor affects the portal vein, SMV with extension into the root of the mesentery and the involvement of the SMV tributaries over a large length, the tumor is also considered inoperable (Figure 3).

CT structured report

The structured CT report in pancreatic ductal adenocarcinoma must include details related to^(2,5):

• location of the tumor (head/body/tail), semiology (hypo-/iso-/hyperdense), degree of enhancement compared to normal pancreatic tissue, and dimensions of the tumor;
• existence of a cleavage plane compared to adjacent anatomical structures;
• bile ducts and pancreatic duct aspects;
• the aspect of the remaining pancreatic tissue;
• adenopathies – location, number, their diameter in the short axis;
• metastases – location, number, dimensions;
• the aspect of the peritoneum, the presence of ascites;
• vascular involvement (arterial and venous) must be quantified (if it is below 50% or above 50% of the circumference), with the analysis of celiac trunk, superior mesenteric artery, common hepatic artery, other arterial structures; superior mesenteric vein specifying the length of tumoral infiltration, portal vein, and other venous structures;
• the presence of vascular thrombosis (arterial or venous);
• the presence of venous collaterals;
• anatomical variants of vascular structures;
• extensive arterial atheromatous changes.

What does the clinician must know? If the pancreatic ductal adenocarcinoma is resectable, borderline or unresectable (Table 1)^(1-8).

Differential diagnostic

Imaging differential considerations in pancreatic ductal adenocarcinoma include: acute and chronic pancreatitis, autoimmune pancreatitis, other pancreatic neoplasms, lymphoma, CBD cholangiocarcinoma, periampullary tumors, pancreatic metastasis⁽⁶⁾.

Conclusions

Computed tomography is the preferred imaging modality for pancreatic tumor staging. The structured CT report, in correlation with the patient’s clinical-biological status and the CA 19-9 value, represents the foundation for a multidisciplinary personalized therapeutic decision for each case.   

Corresponding author: Ioana G. Lupescu E-mail: ioana.lupescu@umfcd.ro

Conflict of interest: none declared.

Financial support: none declared.

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