Pancreatic Adenocarcinoma Imaging: What You Need to Know

Pancreatic cancer is the fourth leading cause of cancer death in the United States^[1] after lung/bronchial, colorectal, and female breast cancers.^[2] The National Cancer Institute (NCI) estimates there will be about 46,420 new cases of pancreatic cancer in 2014 (2.8% of all new cancer cases), with approximately 39,590 deaths from this disease (6.8% of all cancer deaths).^[2] Of the exocrine pancreatic tumors, pancreatic adenocarcinoma is the most common primary malignant tumor, accounting for approximately 80%-95% of nonendocrine pancreatic neoplasms.^[3] It affects men twice as often as women, with a mean age of onset of 55 years. This coronal contrasted computed tomography (CT) scan demonstrates a large adenocarcinoma that is centered within the head of the pancreas.

Image courtesy of Radiopaedia/Drs. Yuranga Weerakkody and Frank Gaillard.

Pancreatic adenocarcinoma has a stealthy presentation, and patients are usually asymptomatic until late in the disease course. If the tumor is present in the head of the pancreas near the biliary system, patients typically present with obstructive jaundice and weight loss; they may or may not have pain. The triad of painless jaundice with a distended, palpable gallbladder (Courvoisier sign) is suggestive of pancreatic malignancy.^[4] This axial CT scan demonstrates a distended, palpable gallbladder in a patient with pancreatic adenocarcinoma. If the tumor is located in the body or tail of the pancreas, patients may not present with signs/symptoms until metastases are present.

Image courtesy of Radiopaedia/Dr. Chris O'Donnell.

Although pancreatic adenocarcinoma may affect anyone, several risk factors have been described. Approximately 5%-10% of cases are believed to be due to hereditary conditions, such as hereditary pancreatitis, Gardner syndrome, familial colon cancer, and others.^[3] Individuals with these unmodifiable risk factors may benefit from screening. Modifiable risk factors include smoking, diabetes mellitus, a high-fat diet, and chronic pancreatitis.^[2] This illustration demonstrates a mass centered within the pancreatic head that is not only obstructing the common bile duct and pancreatic duct but also invading the duodenum.

Image courtesy of Radiology Assistant/Drs. Otto van Delden and Robin Smithuis.

Most pancreatic adenocarcinomas are well to moderately differentiated, and well-developed glandular structures that resemble normal pancreatic ducts are embedded in the desmoplastic stroma.^[5] However, the degree of differentiation can also vary in the same tumor—from well-formed to partially formed glands, to poorly oriented singly infiltrating cells, to solid sheets of neoplastic cells^[5,6]—which can make it difficult to histologically differentiate between neoplastic glands and benign reactive glands of chronic pancreatitis.^[6] Features indicative of invasive carcinoma are shown.^[6]

Image adapted from Hruban RH, Fukushima N. Pancreatic adenocarcinoma: update on the surgical pathology of carcinomas of ductal origin and PanINs. Mod Pathol. 2007;20(suppl 1):S61-70. PMID: 17486053.^[6]

Other conditions to consider in the differential diagnosis of patients with suspected pancreatic cancer include neuroendocrine tumors, pancreatic lymphoma, gastric lymphoma, benign pancreatic cysts, intraductal papillary mucinous neoplasm, and autoimmune pancreatitis. This image shows features suggestive of pancreatic adenocarcinoma, including prominent honeycombing, disorganization, nuclear overlap, and lack of uniform nuclear spacing; the patient's other clinical, imaging, and cytologic findings were also indicative of malignancy.

Image courtesy of Flickr/Ed Uthman, MD.

Transabdominal ultrasonography is the least sensitive of the various imaging modalities that can be used to detect pancreatic lesions, but it is widely available and inexpensive.^[7,8] Thus, this is often the first-line imaging study in the evaluation for pancreatic cancer, and clinicians must be familiar with the appearance of a pancreatic mass on sonograms. Lesions in the pancreatic body or tail may not be seen on sonograms, as this area of the pancreas is often poorly evaluated owing to the presence of overlying bowel gas. This grayscale sonogram demonstrates a hypoechoic mass in the pancreatic head that is obstructing the pancreatic duct.

Image courtesy of Radiology Assistant/Drs. Otto van Delden and Robin Smithuis.

Endoscopic ultrasonography (EUS) provides images of the pancreas without interference by bowel gas. The sensitivity of EUS for detecting small pancreatic masses has been reported to be as high as 98%,^[9] and this modality can be used to concurrently assess for portal and splenic venous invasion. This EUS image through the pancreatic head demonstrates a hypoechoic mass (both arrows) that is obstructing the common bile duct (left arrow).

Image courtesy of Radiology Assistant/Drs. Otto van Delden and Robin Smithuis.

EUS also allows for image-guided biopsy of a suspicious pancreatic mass, which is performed by using fine needle aspiration (FNA) to obtain samples from the tumor. This image demonstrates the hyperechoic needle tip (arrow) centered within a hypoechoic pancreatic mass.

Image courtesy of Medscape/Dr. Klaus Mergener.

Continued improvement in CT technology has made it one of the initial comprehensive imaging modalities for evaluation of pancreatic adenocarcinoma.^[10] The typical appearance of the tumor on CT scan is that of an irregular, hypovascular mass with abrupt obstruction of the pancreatic and/or common bile duct. Approximately 60%-70% of pancreatic adenocarcinomas are located in the head of the pancreas.^[3,6] This axial CT image demonstrates a subtle hypoattenuating lesion in the pancreatic head/uncinate process.

Image courtesy of Radiopaedia/Drs. Yuranga Weerakkody and Frank Gaillard.

CT scanning is widely used to stage pancreatic cancer, because the extent of the disease dictates whether or not the tumor can be removed surgically. The goal in staging by CT scan is to evaluate for local invasion of the tumor into the adjacent soft tissues and/or vasculature as well as to detect the presence of any metastases. This CT scan shows a normal pancreas and demonstrates the intimate contact the pancreas has with the adjacent bowel and vascular structures. IVC = inferior vena cava.

Image courtesy of Radiology Assistant/Drs. Otto van Delden and Robin Smithuis.

Evaluation for local invasion includes assessing the soft tissues of the adjacent duodenum, stomach, spleen, and left adrenal gland. Clinicians should also assess for the presence of metastatic disease, which may include examining the adjacent periportal lymph nodes, the liver, the peritoneum, and more distant sites such as the lungs, pleura, and bones. This axial CT scan demonstrates multiple soft-tissue implants along the peritoneum (arrowheads), which are consistent with metastases from the patient's primary pancreatic adenocarcinoma.

Image courtesy of Radiology Assistant/Drs. Otto van Delden and Robin Smithuis.

Evaluation of the adjacent vasculature is important, including the superior mesenteric artery (SMA) and vein (SMV) and the portal and splenic veins, because pancreatic tumors are unresectable if metastases are present, if there is vessel involvement in which the SMV is completely occluded and reconstruction is not possible, or when there is more than 180° involvement of the celiac artery or SMA. Involvement of the splenic artery does not preclude resection. If the tumors are resectable, preoperative evaluation of normal vascular variants is crucial to avoid complications of intraoperative vascular injury.^[7] This coronal CT scan demonstrates narrowing and encasement of the portal vein by a pancreatic mass.

Image courtesy of Medscape/Dr. Zahir Amin.

Magnetic resonance imaging (MRI) is most often used as a problem-solving imaging modality. Tumors demonstrate low signal on T1-weighted images due to their fibrous nature, and the masses hypoenhance in a manner similar to that seen on CT scans. MRI, particularly magnetic resonance cholangiopancreatography (MRCP), is especially good for showing normal and variant biliary and pancreatic ductal anatomy. Pancreatic adenocarcinoma often obstructs the pancreatic and/or the common bile duct and results in dilatation; when both ducts are affected, this is referred to as the "double duct sign," as shown on this coronal MRCP maximum intensity projection.

Image courtesy of Radiopaedia/Dr. Henry Knipe and Radswiki.

The use of positron emission tomography (PET) combined with CT scanning (PET/CT) for staging pancreatic cancer is controversial given the limited data on its use in this disease. However, some clinicians utilize this imaging modality to follow treatment responses in nonsurgical patients or to evaluate for subtle hypermetabolic metastases that cannot be seen on CT images.^[10] On PET/CT images, the tumors usually take up fluorodeoxyglucose ("FDG avid") and accumulate the radiotracer. These images demonstrate an FDG-avid pancreatic mass that was later proven to be adenocarcinoma. An FDG-avid supraclavicular lymph node that is consistent with metastasis is also noted (image A, top arrow).

Images reprinted with permission from Springett GM, Hoffe SE. Borderline resectable pancreatic cancer: on the edge of survival. Cancer Control. 2008;15(4):295-307. PMID: 18813197.

Treatment for pancreatic adenocarcinoma depends on whether or not preoperative imaging studies demonstrate a resectable tumor. Complete surgical resection for pancreatic head masses may be performed by a pancreaticoduodenectomy (Whipple procedure). A distal pancreatectomy may be performed for tumors that are localized to the pancreatic body/tail and are without metastases. External beam radiation and chemotherapy may be employed as neoadjuvant, definitive, or adjuvant treatment strategies. This gross pathology specimen demonstrates a yellow fibrous adenocarcinoma in the pancreatic head that is adherent to the adjacent duodenum.

Image courtesy of Radiopaedia/Drs. Yuranga Weerakkody and Frank Gaillard.

Imaging also plays an important role in postsurgical patients for the detection of local recurrence or metastatic disease. It can also be used to follow progression of the disease or response to treatment in nonsurgical patients undergoing chemotherapy and/or radiation for pancreatic adenocarcinoma. This CT scan demonstrates adenocarcinoma of the pancreatic tail with metastases to the liver and left adrenal gland.

Image courtesy of Radiopaedia/Dr Roberto Schubert.

Unfortunately, pancreatic adenocarcinoma has a poor prognosis, with an overall survival of less than 6%, although the 5-year survival rate with surgery for localized pancreatic cancer may be as high as 18%-24%.^[1] Primary prognostic factors include whether or not the tumor is localized and can be completely resected and whether or not it has metastasized.^[1] The greatest survival rates are in those whose tumors are found early and are resectable; approximately 20% of patients have resectable tumors at the time of presentation.^[7] Patients with pancreatic cancer are also prone to complications such as venous thrombosis, gastrointestinal hemorrhage, infections, bowel obstruction, and intra-abdominal abscesses or fistulae.^[11] This coronal CT scan demonstrates a large heterogeneous mass within the pancreatic head that is causing marked obstruction of the extrahepatic and intrahepatic biliary ducts.

Image courtesy of Radiopaedia/Drs. Yuranga Weerakkody and Frank Gaillard.