Imaging diagnosis and staging of pancreatic ductal adenocarcinoma: a comprehensive review

Abstract

Pancreatic ductal adenocarcinoma (PDAC) has continued to have a poor prognosis for the last few decades in spite of recent advances in different imaging modalities mainly due to difficulty in early diagnosis and aggressive biological behavior. Early PDAC can be missed on CT due to similar attenuation relative to the normal pancreas, small size, or hidden location in the uncinate process. Tumor resectability and its contingency on the vascular invasion most commonly assessed with multi-phasic thin-slice CT is a continuously changing concept, particularly in the era of frequent neoadjuvant therapy. Coexistent celiac artery stenosis may affect the surgical plan in patients undergoing pancreaticoduodenectomy. In this review, we discuss the challenges related to the imaging of PDAC. These include radiological and clinical subtleties of the tumor, evolving imaging criteria for tumor resectability, preoperative diagnosis of accompanying celiac artery stenosis, and post-neoadjuvant therapy imaging. For each category, the key imaging features and potential pitfalls on cross-sectional imaging will be discussed. Also, we will describe the imaging discriminators of potential mimickers of PDAC.

Keywords: Computed tomography; Magnetic resonance imaging; Pancreatic cancer; Treatment response; Tumor resectability.

Fig. 1

A 72-year-old man with isoattenuating PDAC. Axial pancreatic phase CT image (a) shows MPD stricture (arrow) at the pancreatic body without visible mass. Transverse transabdominal ultrasound image (b) shows a hypoechoic mass (asterisk) at the site of MPD stricture (arrow). Dynamic contrast-enhanced MR images using fat-suppressed T1-weighted sequence in the arterial (c) and portal venous (d) phases show MPD stricture (arrow) but fail to demonstrate a distinct mass. Subsequent pancreaticoduodenectomy revealed PDAC

Fig. 2

A 72-year-old man with PDAC. Axial portal venous phase CT image (a) shows MPD stricture (arrow) at the pancreatic body with upstream dilatation without visible obstructing mass. Axial portal venous phase CT images (b and c) obtained 6 months later show the progression of the MPD stricture (arrow) with worsened upstream ductal dilatation and pancreatic atrophy. There is a small hypoattenuating mass (arrowheads in c) associated with an enlarged necrotic metastatic portacaval lymph node (asterisk)

Fig. 3

A 63-year-old man with locally advanced PDAC in uncinate process. Axial pancreatic phase CT images (a and b) show a mass (arrowhead) in the uncinate process encasing SMA with mild upstream dilatation of CBD (arrow) and MPD (short arrows) and associated with mildly distended gallbladder (GB)

Fig. 4

A 63-year-old man with uncinate process PDAC causing a duodenal obstruction. Axial pancreatic phase CT images (a and b) show a hypoattenuating mass (asterisk) arising from the uncinate process, infiltrating the third part of the duodenum (D) and abutting the anterior wall of the aorta. CBD (arrow) is normal in caliber. The pancreas (P) has no ductal dilatation or atrophy. Axial portal venous phase CT image (c) obtained 1 month later shows a marked distension of the stomach (S) due to duodenal obstruction and there is a new hypoattenuating metastatic liver lesion (arrow)

Fig. 5

A 47-year-old man with uncinate process PDAC. Axial (a) and coronal (b) pancreatic phase CT images show a small hypoattenuating mass (arrowheads) in the uncinate process of the pancreas. Due to the location of the tumor, there is no CBD or MPD dilatation. EUS-guided biopsy revealed PDAC and the patient underwent pancreaticoduodenectomy

Fig. 6

A 63-year-old man with PDAC. Axial pancreatic phase CT images (a and b) show a hypoattenuating mass (asterisk) in the pancreatic head with > 180° tumor contact with a replaced right hepatic artery (long arrow) and > 180° tumor contact with SMV (short arrow) with deformity of the vein lumen. The patient underwent a total pancreatectomy and vascular reconstruction after neoadjuvant therapy, but liver metastases developed one year after surgery

Fig. 7

A 64-year-old man with PDAC of the head. Coronal T2-weighted MR image (a) shows a large low-intermdiate signal intensity pancreatic head mass (asterisk) causing upstream CBD dilatation (long arrow). Axial contrast-enhanced T1-weighted image in the portal venous phase (b) shows a hypoenhancing pancreatic head mass abutting SMV. Coronal (c) and axial (d) portal venous phase CT images obtained 2 months later after neoadjuvant therapy show a significant reduction of the tumor bulk (short arrows). The patient subsequently underwent pancreaticoduodenectomy, and pathology revealed extensive neoadjuvant treatment effect on PDAC with only 1 cm residual tumor and negative resection margin. No recurrence has been reported for 3 years

Fig. 8

A 62-year-old woman with PDAC of the head. Axial portal venous phase CT images (a and b) show an ill-defined hypoattenuating mass encasing SMA (long arrow). SMV demonstrates a teardrop sign (short arrow) and is completely obliterated at a higher level (not shown). Axial portal venous phase CT images (c and d) obtained 2 months after neoadjuvant therapy show interval reduction of the tumor size and tumor contact with SMA (long arrow) and SMV (short arrow). The patient underwent pancreaticoduodenectomy and pathology revealed no residual invasion to SMA

Fig. 9

A 60-year-old man undergoing preoperative imaging for PDAC. Axial (a and b), and sagittal (c) pancreatic phase CT images show ostial stenosis of the celiac artery (arrow) due to atherosclerotic disease. The patient has a biliary stent (curved arrow) and PDAC is identified as a subtle hypoattenuating lesion (arrowheads). Axial fat-suppressed T1-weighted MR image (d) clearly demonstrates PDAC as a hypointense mass. Intraoperative Doppler ultrasound (e and f) shows a significant celiac artery stenosis by demonstrating caudocranial/reversed blood flow in the gastroduodenal artery, denoting its significant contribution to the hepatic arterial supply. The patient subsequently underwent pancreaticoduodenectomy after celiac artery stenting

Fig. 10

A 71-year-old man with a mass-forming AIP. Axial (a–c) pancreatic phase CT images show two ill-defined, mass-like lesions (asterisk) in the pancreatic body without significant MPD dilatation (arrows). There is associated rind of periaortic soft tissue thickening (arrowheads) representing IgG4-related retroperitoneal fibrosis

Fig. 11

A 60-year-old woman with a segmental form of groove pancreatitis. Coronal portal venous phase CT image (a) shows a hypoattenuating sheet-like area in the pancreaticoduodenal groove (between long arrows) associated with mural thickening and luminal narrowing of the descending duodenum. CBD (short arrow) is displaced medially by the inflammatory process and tapers distally. MR images with coronal T2 HASTE sequence (b), axial fat-suppressed T1 sequence (c), and axial contrast-enhanced fat-suppressed T1 sequence of the delayed phase (d) show the pancreaticoduodenal groove abnormality (between long arrows) containing multiple tiny cysts along the duodenal wall with high T2-signal intensity and a sheet of fibro-inflammatory tissue with low T1-signal intensity, and delayed enhancement. Non-enhancing tiny pseuodocyst is noted (curved arrow). CBD (short arrow) and MPD (arrowhead) are not dilated. The patient has improved on subsequent follow-up

Fig. 12

A 39-year-old woman with focal fat infiltration of the pancreatic head. Axial portal venous phase CT image (a) show low-attenuation area (arrows) in the pancreatic head with a tongue-like extension just posterior to SMV. No mass effect or MPD dilatation. Note the normal attenuation parenchyma around the CBD. Axial chemical shift MR images show no abnormality at in-phase sequence (b) and drop of signal of the same area (arrows) at opposed phase sequence (c) consistent of microscopic fat in focal fat infiltration

Fig. 13

A 53-year-old man with a pancreatic neuroendocrine tumor of the head. Axial arterial phase (a) and portal venous phase (b) and (c) CT images show a well-defined mass (asterisk) with peripheral hypervascularity and central cystic area. Only mild dilatation of the MPD (arrow) due to external compression by the tumor, rather than ductal origin of the tumor. Histopathology revealed pancreatic endocrine tumor

Fig. 14

A 72-year-old man with papillary thyroid cancer metastasis involving the pancreas. Axial pancreatic phase CT image shows multiple enhancing masses (asterisks) involving the entire pancreas