1. Pancreatic adenocarcinoma
Pancreatic adenocarcinoma (PA) usually appear as low attenuating masses in the pancreatic and portal venous phases. These lesions typically accompany pancreatic duct dilatation with abrupt narrowing. (figure 1)
Fig. 1: T2-weighted MR image shows cut-off p-duct (yellow arrow). Dynamic contrast-enhanced Magnetic resonance , arterial, portal, delayed MR images demonstrate ill-defined infiltrative mass lesion (blue arrow) in pancreas body and progressive enhancement with hypovascular core (red arrow).
References: Department of Radiology, Dong-A university medical center, Busan, Republic of Korea
Major feature
- Age/Sex : >60 years, Male>Female
- Enhancing pattern : progressive enhancement with hypovascular core
- P-duct morphology : pancreatic duct abrupt cut-off or dilatation
Ancillary feature
- Increased CA19-9
- Infiltrative border
Fig. 2: 79-year-old woman with jaundice, elevated CA-19-9.
(A) T2-weighted MR image shows cut-off p-duct (arrow). Dynamic contrast-enhanced Magnetic resonance , arterial (B), portal (C), delayed (D) MR images demonstrate ill-defined infiltrative mass lesion in pancreas neck portion and progressive enhancement with hypovascular core (arrowshead).
References: Department of Radiology, Dong-A university medical center, Busan, Republic of Korea
2. Inflammatory mimics
Focal autoimmune pancreatitis (IgG4-related)
Autoimmune pancreatitis (AIP) is an uncommon form of chronic pnacreatitis caused by autoimmune mechanism. It is one of the most frequent misdiagnosing lesion with the suspicion of PA.
Diffuse "sausage-like" parenchymal enlargement with effacement of the lobular contour of pancreas and capsule-like rim enhancement are typical radiologic features of autoimmune pancreatitis. Another clue for diagnosis of AIP is involvement of an extra-pancreatic organ such as the biliary tree, retroperitoneum, salivary gland, or kidney.
Patch inhomogeneous enhancement in the pancratic phase and homogeneous enhancement in the late phase are features of focal AIP. (figure 3)
Fig. 3: Contrast enhanced portal phase CT image shows heterogeneous mass like lesion in pancreas head portion. Dynamic contrast-enhanced Magnetic resonance, arterial, portal MR images demonstrates delayed homogeneous enhancement (blue arrow). T2-weighted MR image shows P-duct penetration sign (orange arrow).
References: Department of Radiology, Dong-A university medical center, Busan, Republic of Korea
Major feature
- Age/Sex : >60 years, Male
- Enahncing pattern : delayed homogeneous enhancement
- P-duct morphology : pancreatic duct penetration sign
Ancillary feature
- Elevated serum IgG or IgG4 level
- Multifocal stricture of the pancreatic duct
- Low diffuse coeffient on DWI
- Involvement of and extra-pancreatic organ
Fig. 4: A 67-year-old man with jaundice, elevated serum IgG4 level
(A) Contrast enhanced portal phase CT image shows heterogeneous mass like lesion in pancreas head portion. Dynamic contrast-enhanced Magnetic resonance, arterial (B), portal (C) MR images demonstrate delayed homogeneous enhancement. T1-weighted MR image (D) shows P-duct penetration sign (arrow).
References: Department of Radiology, Dong-A university medical center, Busan, Republic of Korea
Mass forming chronic pancreatitis
Chronic pancreatitis is characterized by dilatation of the main pancreatic duct, parenchymal atrophy, pancreatic calcifications. Differentiation between chronic pancreatitis and PA is challenging when the former presents as focal mass without calcifications.
Mass forming chronic pancreaitis shows hypo-to-iso intense T1-weighted signal intensity reflecting chronic inflammation and fibrosis. And it is mostly show iso-to-hyper intensity on T2-weighted images. Variable dynamic patterns are shown with loss of normal early homogeneous pancreatic enhancement. (figure 5)
Fig. 5: T1-weighted MR image shows low-to-iso signal intensity mass like lesion in pancreatic head portion (blue arrow). Dynamic contrast-enhanced Magnetic resonance, arterial, delayed phase MR images demonstrate sudden delay enhancement (red arrow). T2-weighted MR image shows P-duct penetration sign (orange arrow).
References: Department of Radiology, Dong-A university medical center, Busan, Republic of Korea
Major feature
- Age/Sex : relatively young, Male > Female
- Enhancing pattern : sudden portal or delay enhancement
- P-duct morphology : pancreatic duct penetration sign
Ancillary feature
- Iso or high SI compared to spleen on T1WI
- Unclear boundaries of the lesions
- Underlying biliary disease or alcohol abuse Hx.
Fig. 6: A 51-year-old men with abdominal pain, history of alcoholic
(A) T1-weighted MR image shows low-to-iso signal intensity mass like lesion with cyst in pancreatic tail portion (arrow). Dynamic contrast-enhanced Magnetic resonance, arterial (B), delayed phase (C) MR images demonstrate sudden delay enhancement. T2-weighted MR image (D) shows P-duct penetration sign (arrowhead).
References: Department of Radiology, Dong-A university medical center, Busan, Republic of Korea
Groove pancreatitis
Groove pancreatitis is an uncommon type of pancreatitis affecting the pancreaticoduodenal groove, defeined as the potential space between the pancreatic head, common bile duct, and duodenum.
On CT, groove pancreatitis presents as ill-defined lesions between the pancreatic head and the duodenum. It can be described as sheet-like curviliear appearance and delayed enhancement. Additionally, presence of cystic dystrophy in the duodenal wall and smooth bile duct narrowing are suspicious findings of groove pancreatitis. (figure 7)
Fig. 7: Contrast enhanced portal phase axial CT image shows a ill-defined mass like lesion in the pancreaticoduodenal groove (blue arrow). Dynamic contrast-enhanced Magnetic resonance, arterial, delayed phase MR images demonstrate delayed enhancement. T2-weighted MR image shows internal cystic change (yellow arrow).
References: artment of Radiology, Dong-A university medical center, Busan, Republic of Korea
Major feature
- Age/Sex : relatively young ( Female
- Enhancing pattern : delay enhancement or patch enhancement
- P-duct morphology : smooth tapered pancreatic duct
Ancillary feature
- Internal cystic change
- Focal thickening and increased enhancement of the second portion of the duodenum
- Soft tissue in the groove
Fig. 8: A 55-year-old man with recurrent postprandial nausea, vomiting
(A) Contrast enhanced arterial phase axial CT image shows a smooth tapered pancreatic duct. Contrast enhanced portal phase axial (B),(C), coronal(D) CT image shows a hypoattenuating area in the pancreaticoduodenal groove (arrow) and irregular wall thickening in duodenal 2nd portion (arrowheads).
References: Department of Radiology, Dong-A university medical center, Busan, Republic of Korea
Table 1: Table 1. Summary of differential diagnostic points between PA and inflammatory mimics.
References: Department of Radiology, Dong-A university medical center, Busan, Republic of Korea
3. Neoplastic mimics
Neuroendocrine tumor
Pancreatic NETs originate from the islet cells of Langerhans and are divided into low-, intermediate-, and high-grade according to the World Health Organization classification. High-grade pancreatic NET can mimic PA on images.
Pancreatic NET usually show solid masses that avidly enhance in the arterial phase. These are well demarcated and do not show pancreatic duct dilatation. (figure 9)
Fig. 9: Contrast enhanced arterial phase axial CT image shows a well-circumscribed enhancing mass in pancreas body portion (blue arrow). T1-weighted MR image shows low signal intensity well-circumscribed mass. T2-weighted MR image, this mass shows high signal intensity. Dynamic contrast-enhanced arterial phase MR images demonstrate avid arterial enhancement (red arrow). Magnetic resonance cholangiopancreatography image shows no pancreatic duct dilatation (orange arrow).
References: Department of Radiology, Dong-A university medical center, Busan, Republic of Korea
Major feature
- Age/Sex : 51~57 years, Male=Female
- Enhancing pattern : avid arterial enhancement
- P-duct morphology : no pancreatic duct dilatation
Ancillary feature
- Well-circumscribed mass
- Calcification
- Liver metastases may be present
Fig. 10: A 77-year-old man with incidental finding
(A) Contrast enhanced arterial phase axial CT image shows a small well-circumscribed enhancing mass in pancreas tail portion (arrow). T1-weighted (B) MR image shows low signal intensity small well-circumscribed mass. T2-weighted (C) MR image, this mass shows high signal intensity. Dynamic contrast-enhanced arterial phase (D) MR images demonstrate avid arterial enhancement.
References: Department of Radiology, Dong-A university medical center, Busan, Republic of Korea
Metastatic cancer
Pancreatic metastases are uncommon and account for 1-2% of all pancreatic neoplasms. The history of another malignancy with pancreatic mass, lack of pancreatic duct dilatation may suggests pancreatic metstases rather than PA. The enhancing pattern can be various due to the vascularity of primary tumor. (figure 11) Also, multiple lesions in other organs can be clue for differentiating with PA.
Fig. 11: Contrast enhanced portal phase axial CT image shows a well-circumscribed mass in pancreas tail portion (arrow). T1-weighted MR image shows low signal intensity well-circumscribed mass. T2-weighted MR image shows iso-to-high signal intensity well-circumscribed mass. Dynamic contrast-enhanced arterial, portal phase MR images demonstrate progressive enhancement.
References: Department of Radiology, Dong-A university medical center, Busan, Republic of Korea
Major feature
- Age/Sex : >60 years, Male>Female
- Enhancing pattern : consistent with primary tumor
- P-duct morphology : no pancreatic duct dilatation
Ancillary feature
- Multiple lesions
- Well circumscribed mass
- Hyperenhancing lesions : renal cancer
- Hypoenhancing lesions : lung cancer
- Lymph node enlargement
Fig. 12: A 78-year-old man with renal cell carcinoma history.
(A) Non-enhanced axial CT image shows a small well-circumscribed mass in pancreas body portion (arrow). T2-weighted (B) MR image shows iso to high signal intensity well-circumscribed mass. Dynamic contrast-enhanced arterial phase (C) MR image demonstrate arterial enhancement. MRCP image (D) shows no pancreatic duct dilatation (arrowhead).
References: Department of Radiology, Dong-A university medical center, Busan, Republic of Korea
Lymphoma
Primary pancreatic lymphoma is rare entity, most likely to be clinically misdiagenosed as PA. Under 2% of all extranodal malignant lymphomas and 0.5% of all pancreatic masses are pancreatic primary lymphoma.
Pancreatic lymphoma show homogeneous enhancing mass in pancreas without vessel invasion. It can encase adjacent vessel with enlarged lymph nodes in pancreatic region. (figure 13)
Fig. 13: Patient with diffuse large B-cell lymphoma history
Contrast enhanced portal phase axial CT images show large mass along pancreas and peripancreatic area with homogeneous enhancement. This mass shows vessel encasement without invasion. Enlarged lymph nodes are shown in peripancreatic area.
References: Department of Radiology, Dong-A university medical center, Busan, Republic of Korea
Major feature
- Age/Sex : >60 years, Male>Female
- Enhancing pattern : homogeneous enhancement
- P-duct dilatation : no pancreatic duct dilatation
Ancillary feature
- Solitary, bulky, homogeneous lesion
- Vessel encasement without invasion
- Enlarged lymph nodes below level of renal veins
Table 2: Tabe 2. Summary of differential diagnostic points between PA and neoplastic mimics.
References: Department of Radiology, Dong-A university medical center, Busan, Republic of Korea