Early Pancreatic Cancers: Pearls, Pitfalls and Mimics

H A Siddiki, MD, J G Fletcher, MD, N Takahashi, MD, J L Fidler, MD, N Dajani, MD, J E Huprich, MD, D M Hough, MD Department of Radiology, Mayo Clinic, Rochester, MN

PURPOSE Overview and Test Cases Discussion Atypical Findings of Pancreatic Cancer Pitfalls in Tumor Detection Pancreatic Cancer Mimics •Autoimmune pancreatitis To display a spectrum of early • Isoattenuating mass • Sub-optimal scanning • Chronic pancreatitis and atypical presentations of • Exophytic tumors • Pancreatitis (acute or chronic) Atypical Findings Mimics

• Perineural and perivascular infiltration • Metastases Isoattenuating Mass . Despite multiphasic, thin section CT, adenocarcinoma of the • Occult neoplasms Autoimmune Pancreatitis (AIP). A1 A2 approximately 10-15% of pancreatic adenocarcinomas are A3 Characteristic imaging findings of AIP • Neoplasms that mimic pancreatic cancer isoattenuating. In such instances secondary signs such as pancreatic without mass • Presence of a stent include diffuse pancreatic enlargement pancreas, in addition to imaging ductal dilation and cutoff, loss of fatty marbling, contour abnormality, or and/or capsule-like rim. Focal mass-like • Intrapancreatic splenule atrophic distal pancreatic parenchyma must be relied upon to visualize • Diffusely infiltrating tumors enlargement of the pancreas is not the mass. Similarly, some pancreatic cancers may demonstrate pitfalls and mimics, in a case- uncommon and may be indistinguishable isointense signal at MR. Case on the right with a 2 cm pancreatic head • Cystic change • Focal fat from pancreatic cancer. Extrapancreatic carcinoma. CT portovenous phase (right images) and MR post contrast based presentation and review. involvement of bile ducts (thickening or LAVA ( left images) show an isointense and isoattenuating mass. enhancement), kidneys (solid masses in Secondary signs of tumor include obstruction of the CBD (as evidenced the cortex), and retroperitoneum fibrosis Case 1. Patient with by stent placement) and pancreatic duct (arrow). are relatively common and often is a clue to the correct diagnosis. In case A, body symptomatic pancreatitis. and tail of pancreas is segmentally B1 B2 B3 Exophytic tumors. Exophytic tumors also enlarged with capsule-like rim (A1). Bile CT and MR imaging are duct wall shows abnormal thickening and account for a large number of missed pancreatic enhancement (A2). Two solid renal available. What are the cancers. These tumors arise peripherally in the cortical nodules are also present (A3). In gland and do not cause typical bile duct or case B, there is a subtle ill-defined low- BACKGROUND findings and diagnosis? pancreatic duct obstruction or atrophy of the distal attenuation area in the head of pancreas pancreas. Case A shows a low attenuation (B1) with dilation of pancreatic duct (B2). nd rounded mass in the uncinate that was missed at There is a subtle low-attenuation lesion in Pancreatic cancer is the 2 most initial review (A1), with A2 demonstrating growth of A1 A2 the cortex of left kidney (B3). This case is B3 difficult to differentiate from carcinoma. common malignant tumor of the GI the mass w ith consequent portal vein and SMA B invasion when the patient became symptomatic 3 C tract, and is the fifth leading cause of Case 7 . What are the findings and diagnosis? months later. The uncinate process should retain Mass-forming chronic pancreatitis may appear as low a sharp angulated margin. Case B shows a density/ intensity mass and can be difficult to differentiate cancer death, with a median survival of cancer arising exophytically off the pancreatic from pancreatic carcinoma. In mass-forming pancreatitis the head posteriorly, while case C shows an exophytic pancreatic duct can often be seen traversing the mass (duct 4 – 6 months. Surgical resection is the penetrating sign), whereas the duct within a carcinoma is often Axial Coronal cancer arising exophytically in the occluded. Evidence of chronic pancreatitis elsewhere in or only chance for cure, with small tumor pancreaticoduodenal groove. Differential w ill around pancreas is helpful. Case A shows a low-signal A1 A2 A3 include groove panctreatitis (see Mimics). intensity area in the neck of pancreas (A1-3) mimicking size being associated with long term pancreatic carcinoma. Pancreatic duct is seen through the low- Perineural and perivascular infiltration without mass. Tumor extension along the neural signal intensity area (duct penetrating sign) (A2). Concurrent B1 survival. Early and small pancreatic plexus is a common finding in pancreatic cancer. In one study it was seen in 91% of patients of CT showed parenchymal calcification (A4) with thick MIP the pancreatic head. Neural plexus invasion can be recognized by soft tissue thickening or MRCP images showing a dilated duct with acinarization (A5). Case B shows a low-attenuation mass in the head of pancreas cancers may present with subtle or stranding around the inferior pancreaticduodenal artery, SMA or celiac artery. While an indistinguishable from pancreatic carcinoma. atypical findings, which if unrecognized, associated pancreatic mass is usually seen, isolated abnormal soft tissue around these vascular A4 A5 structures should alert one of the possibility of an underlying pancreatic malignancy which may be isodense in some cases. will delay diagnosis. Conversely, A1 A3 Metastases to the pancreas are rare occurring in 3-12% of A2 several diseases are often erroneously autopsies, the most frequent sources being renal, lung, breast, melanoma, GI tract, etc…, and can manifest as a solitary mass, confused with pancreatic cancer. Case 2 . What are the findings and your diagnosis? Diffusely infiltrating pancreatic cancers. The normal pattern of diffuse pancreatic enlargement or multiple nodules. The growth for pancreatic cancer is invasion of adjacent local structures. Low enhancement characteristics of the metastases closely resemble attenuation tumor infiltration within the gland can rarely be seen (arrows). the primary malignancy. Images to the left show a metastatic lung Diffusely infiltrating pancreatic cancers can mimic other diseases, which can cancer to the pancreatic head that resulted in biliary and pancreatic Case 8 – What is your differential? What is the next step? affect the entire gland, such as lymphoma, AIP and metastases. ductal obstruction, mimicking a primary pancreatic cancer. B1 B2

Lymphoma typically presents as a large low-density mass. Findings that may help differentiate lymphoma from carcinoma include larger mass size, no ductal dilatation, vessels running through the tumor (B1), lymphadenopathy below the level of the renal veins, normal tumor Cystic Masses – High grade and anaplastic markers and similar masses in other organs (B2) . Imaging Technique pancreatic adenocarcinomas will rarely be cystic in appearance. MR imaging may be helpful, as cystic adenocarcinomas will not exhibit the typical CT Groove pancreatitis is focal chronic homogeneous small cysts of microcystic serous A1 A2 A3 cystadenomas. Their appearance may overlap with pancreatitis affecting the pancreaticoduodenal
Biphasic technique groove forming fibrotic sheet-like soft tissue in the cystic neoplasms with malignant potential (e.g., groove (A1), which typically shows delayed mucinous neoplasms, cystic metastases, cystic islet
Pancreatic phase - ~ 45 sec after injection or enhancement. It commonly results in duodenal cell tumors, etc…). 20 seconds after aortic peak stenosis or tapered stricture of CBD. Cyst Arterial Phase Pancreatic Phase Hepatic Phase formation is common (A3). In this case, the
Hepatic phase - ~ 65 sec after injection or 40 Case 9 – CT enterography performed for abdominal pain. What are pancreas and bile duct are not involved (A2, A3). seconds after aortic peak Case 3. 85 year-old female with breast cancer. What are the the findings and diagnosis? findings and diagnosis?
Slice thickness ≤ 3mm Serous cystadenomas can A1 A2 B1 B2 Pitfalls occasionally appear as solid tumors on
Multiplanar 2D review with 3D problem-solving contrast-enhanced study (A1, B1). T2W I can better demonstrate the internal tiny MR Suboptimal scanning. Surveillance imaging of the abdomen is not cystic components of this neoplasms and optimized to visualize the pancreatic duct or maximize signal differences aid in differentiating this from carcinoma
Axial and coronal SSFSE/HASTE/FIESTA to between the pancreatic parenchyma and tumors. The sensitivity of CT in (A2, B2). detecting pancreatic cancer is related to slice thickness employed. When image the pancreatic and common bile duct clinical suspicion for pancreatic neoplasm is high, dedicated biphasic CT or MR of the pancreas should be obtained--even in the presence of a recent negative Periampullary carcinomas may arise from ampulla, distal bile duct
T1w GRE imaging w/o and with FS surveillance CT employing thicker slice thicknesses. The top row is from a carcinoma, pancreas or duodenum. Periampullary carcinoma is often small and surveillance CT of the abdomen that was interpreted as negative. In retrospect may be difficult to detect on CT or MR, as it presents early with bile duct
Dynamic Gd-enhanced LAVA / VIBE there is subtle dilation of the pancreatic duct in the tail and body of the obstruction. Bile duct stent can obscure periampullary carcinomas. Mass may present predominantly in the duodenal lumen as in this case. Case 10 – Known pancreatic ductal stricture (arrow). What is your pancreas. Dedicated pancreatic imaging was performed one day later (bottom) diagnosis? with thinner slice thickness and biphasic technique, and clearly shows Case 4. Stent placed for biliary pancreatic ductal dilation and cutoff, and presence of a low attenuation mass in obstruction. What are the findings and the pancreatic head. Intrapancreatic splenule appears as a well- A1 A2 A3 circumscribed mass with enhancement and signal your diagnosis? characteristics similar to those of the spleen in all Typical Findings Case 11 – What imaging sequences (A1, A2). It is often mistaken for hypervascular pancreatic tumors, such as islet cell tumors and me tastatic features favor chronic Pancreatitis. Approximately 10% of pancreatic cancers are renal cell carcinomas. The signal of the lesion decreases of Pancreatic Adenocarcinoma associated with pancreatitis, whereas a smaller minority (1 – 2%) of on SPIO-enhanced-T2WI (A3). cases of pancreatitis are due to pancreatic carcinoma. Pancreatitis may pancreatitis over pancreatic also complicate after ERCP or stent placement. The inflammatory A • Mass changes of pancreatitis can mask an underlying pancreatic cancer and cancer? distract the radiologist. Conversely, pancreatitis may mimic carcinoma. A1 A2 A3 Even if the tumor is correctly identified, changes of pancreatitis may Focal fat within the pancreas - attenuation difference (usually hypo- cause over- or under-staging of the pancreatic carcinoma. may mimic low density/ intensity Case A shows a small Stage I pancreatic cancer (red arrow) with post- pancreatic carcinoma (A1) on MR obstructive pancreatitis (green arrow) extending into the uncinate post-contrast images. Presence of process. The findings may be misinterpreted as invasive disease. attenuating compared to the gland) Case B shows a patient with obvious pancreatitis with an enlarged B fat can be confirmed using in-and- pancreatic body and tail and inflammatory changes in the adjacent opposed phase GRE imaging (A2, retroperitoneum. However, the low attenuation mass in the pancreatic A3). - disruption of fatty marbling head (arrow) was not identified until 8 months later. Case C shows changes of post-ERCP pancreatitis. The changes of pancreatitis obscures a subtle iso-attenuating tumor (red arrow) in the • Pancreatic ductal dilation and cutoff pancreatic neck causing pancreatic ductal cutoff, with focal narrowing of the portal vein (green arrow). Case 5. Coronal images from a CT of the chest and abdomen. C • Double duct sign (obstruction of common What are the findings and your diagnosis? CONCLUSIONS bile and pancreatic duct) Occult Neoplasms. Approximately 5% of pancreatic cancers will be occult at CT or MR despite use of appropriate technique. When clinical suspicion is • Radiologists should be aware of atypical findings in • Atrophy of gland upstream to tumor Case 12 - What are the findings and diagnosis? high, endoscopic ultrasound should be performed to exclude a small or intraductal neoplasia. pancreatic cancer, which should not preclude its diagnosis. Common Bile Duct Stent. We believe that presence of a CBD stent may • Signs of locally advanced or distant also affect tumor conspicuity by changing perfusional patterns or streak artifact. When a CBD stent is present, radiologists should assume (in the absence of additional information) that CBD obstruction was present prior to • Radiologists should be aware of potential pitfalls, which disease stent placement. In the case at right, the CBD stent and dilated pancreatic duct should alert the radiologist to the presence of a pancreatic mass, even in the presence of a normal-appearing pancreatic head. This patient had a can lead to a failure to detect pancreatic cancer. • Any combination of these findings pancreatic carcinoma. • Pancreatic cancer mimics can often be distinguished by paying attention to key differential points. Case 6 . What are the findings and your diagnosis?