Diffuse pancreatic ductal adenocarcinoma: Characteristic imaging features

Imaging of pancreatic ductal adenocarcinoma - An update for all stages of patient management

Background

Pancreatic ductal adenocarcinoma (PDAC) is a common and lethal cancer. From diagnosis to disease staging, response to neoadjuvant therapy assessment and patient surveillance after resection, imaging plays a central role, guiding the multidisciplinary team in decision-planning.

Review aims and findings

This review discusses the most up-to-date imaging recommendations, typical and atypical findings, and issues related to each step of patient management. Example cases for each relevant condition are presented, and a structured report for disease staging is suggested.

Conclusion

Despite current issues in PDAC imaging at different stages of patient management, the radiologist is essential in the multidisciplinary team, as the conveyor of relevant imaging findings crucial for patient care.

Diffuse-Type Pancreatic Ductal Adenocarcinoma Mimicking Autoimmune Pancreatitis

Pancreatic ductal adenocarcinoma (PDAC) classically presents as a solitary mass on cross-sectional imaging. Diffuse-type PDAC is an unusual variant that accounts for 1%-5% of PDACs. Owing to its rarity, there are no established radiographic or endosonographic definitions. We report a unique case of diffuse-type PDAC presenting with imaging findings of 2 distinct masses in the pancreatic head and tail and with endoscopic ultrasound findings of diffuse gland enlargement mimicking autoimmune pancreatitis. The case illustrates the importance of sampling several areas of the pancreas when diffuse enlargement is present on endoscopic ultrasound and multiple masses are seen on cross-sectional imaging.

Systematic review and meta-analysis of MRI features for differentiating autoimmune pancreatitis from pancreatic adenocarcinoma

OBJECTIVES

To identify reliable MRI features for differentiating autoimmune pancreatitis (AIP) from pancreatic ductal adenocarcinoma (PDAC) and to summarize their diagnostic accuracy.

METHODS

We conducted a systematic literature review and meta-analysis using PubMed, EMBASE, and the Cochrane Library to identify original articles published between January 2006 and July 2021. The pooled diagnostic accuracy, including the diagnostic odds ratios (DORs) with 95% confidence intervals (CIs) of the identified features, was calculated using a bivariate random effects model.

RESULTS

Twelve studies were included, and 92 overlapping descriptors were subsumed under 16 MRI features. Ten features favoring AIP were diffuse enlargement (DOR, 75; 95% CI, 9-594), capsule-like rim (DOR, 52; 95% CI, 20-131), multiple main pancreatic duct (MPD) strictures (DOR, 47; 95% CI, 17-129), homogeneous delayed enhancement (DOR, 46; 95% CI, 21-104), low apparent diffusion coefficient value (DOR, 30), speckled enhancement (DOR, 30), multiple pancreatic masses (DOR, 29), tapered narrowing of MPD (DOR, 15), penetrating duct sign (DOR, 14), and delayed enhancement (DOR, 13). Six features favoring PDAC were target type enhancement (DOR, 41; 95% CI, 11-158), discrete pancreatic mass (DOR, 35; 95% CI, 15-80), upstream MPD dilatation (DOR, 13), peripancreatic fat infiltration (DOR, 10), upstream parenchymal atrophy (DOR, 5), and vascular involvement (DOR, 3).

CONCLUSION

This study identified 16 informative MRI features to differentiate AIP from PDAC. Among them, diffuse enlargement, capsule-like rim, multiple MPD strictures, and homogeneous delayed enhancement favored AIP with the highest DORs, whereas discrete mass and target type enhancement favored PDAC.

KEY POINTS

• The MRI features with the highest pooled diagnostic odds ratios (DORs) for autoimmune pancreatitis were diffuse enlargement of the pancreas (75), capsule-like rim (52), multiple strictures of the main pancreatic duct (47), and homogeneous delayed enhancement (46). • The MRI features with the highest pooled DORs for pancreatic ductal adenocarcinoma were target type enhancement (41) and discrete pancreatic mass (35).

Diffuse Involvement of Pancreas is not Always Autoimmune Pancreatitis

RATIONALE AND OBJECTIVES

To determine the prevalence of diffuse involvement of pancreas and to identify the findings of malignancies using enhancement computed tomography (CT).

MATERIALS AND METHODS

A total of 1,0249 patients performed enhancement CT in our hospital over 62 months were investigated and the final study cohort includes 245 patients (170 males, 75 females; mean age, 56.94 ± 12.17 years). The reference standard is the final clinical/pathological diagnosis. The lesion-to-aorta enhancement ratio (LAR) on the pancreatic arterial phase, portal phase and delayed phase (DP) and the traditional CT findings were evaluated. Intergroup comparisons between malignancies and non-malignancies lesions were performed. Univariate and multivariate analyses were conducted to identify findings predicting malignancies.

RESULTS

The prevalence of malignancy was 45.3% (111/245) of diffuse enlargement of pancreas. All benign lesions were autoimmune pancreatitis 54.7% (n = 134). The most common malignant lesion was pancreatic ductal adenocarcinoma (n = 88, 35.9%). Other rare lesions with malignant potential included pancreatic neuroendocrine tumor (n = 11, 4.5%), lymphoma (n = 4, 1.6%), metastasis (n = 4, 1.6%), solid pseudopapillary neoplasm (n = 3, 1.2%) and acinar cell carcinoma (n = 1, 0.4%). Residual normal pancreas parenchyma, heterogeneity, short axis (cut-off value, 3.15 cm) and LARDP (cut-off value, 0.75) were independent predictors of malignancies. When the above predictors were combined, a sensitivity of 94.2%, a specificity of 90.8% were attained.

CONCLUSION

Diffuse involvement of the pancreas is rare and is not a specific sign of autoimmune pancreatitis, and it is associated with a wide spectrum of malignant conditions. Dynamic enhancement CT is helpful to identifying malignancies.

MRI features for differentiation of autoimmune pancreatitis from pancreatic ductal adenocarcinoma: A systematic review and meta-analysis

BACKGROUND AND AIMS

The accurate differential diagnosis between autoimmune pancreatitis (AIP) and pancreatic ductal adenocarcinoma (PDAC) is clinically important. We aimed to determine significant MRI features for differentiating AIP from PDAC, including assessment of diffusion-weighted imaging (DWI).

METHODS

We performed a systematic search using three databases. The pooled diagnostic odds ratio was calculated using a bivariate random effects model to determine significant MRI features for differentiating AIP from PDAC. The pooled sensitivity and specificity were calculated. The qualitative systematic review for DWI assessment was performed.

RESULTS

Of nine studies (775 patients), multiple main pancreatic duct (MPD) strictures, absence of upstream marked MPD dilatation, peripancreatic rim, and duct penetration sign were significant MRI features for differentiating AIP from PDAC. Absence of MPD dilatation had the highest pooled sensitivity (87%, 95% CI=68-96%), whereas peripancreatic rim had the highest pooled specificity (100%, 95% CI=88-100%). Of 12 studies evaluating DWI, seven reported statistically significant differences in apparent diffusion coefficient (ADC) values between AIP and PDAC; however, four reported lower ADC values in AIP than in PDAC, but three reported the opposite result.

CONCLUSION

The four significant MRI features can be useful to differentiate AIP from PDAC, but DWI assessment might be limited.

Atypical and uncommon CT and MR imaging presentations of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinomas (PDACs) occasionally have atypical and uncommon imaging presentations that can present a diagnostic dilemma and result in false interpretation. This article aimed to illustrate these CT and MR imaging findings, including isoattenuating PDAC, coexisting acute pancreatitis, PDAC with a cystic feature, groove PDAC, diffuse PDAC, hypointensity on diffusion-weighted imaging (DWI), multifocal PDAC, intratumoral calcification, and extrapancreatic invasion with a barely discernable mass. A subset of PDACs with atypical features are occasionally encountered during routine clinical practice. Knowledge of and attention to these atypical and uncommon variable imaging features may allow radiologists to avoid misinterpretation and a delayed diagnosis.

Diffuse Pancreatic Carcinoma with Hepatic Metastases

Pancreatic cancer is one of the seven leading causes of cancer death worldwide. Diffuse pancreatic carcinoma is very rare and underreported in the literature. Many advances have been made in the diagnosis and management of pancreatic cancer. However, most pancreatic cancer cases are detected at the terminal or metastatic stages. Therefore, timely diagnosis and therapeutic management are desirable goals for this disease. Although the proliferation of pancreatic cancer has been reduced by intervention, more work is needed to treat and prevent the disease. The purpose of this article is to present a case of a 54-year-old male with pancreatic cancer and to review the epidemiology, diagnosis, management, and prevention of pancreatic tumors in general as well as pancreatic carcinoma in particular.

Comprehensive histological evaluation with clinical analysis of venous invasion in pancreatic ductal adenocarcinoma: From histology to clinical implications

OBJECTIVES

Venous invasion is a poor prognostic factor for pancreatic ductal adenocarcinoma (PDAC). However, our understanding of various features of venous invasion is limited. Our aim is to comprehensively evaluate various histopathologic features of venous invasion, including status, type (lymphatic or venous), number of invasion foci, and histologic pattern (pancreatic intraepithelial neoplasia [PanIN]-like, conventional) in PDACs.

METHODS

Various features of venous invasion, including status, number of invasion foci, histologic patterns [pancreatic intraepithelial neoplasia (PanIN)-like, conventional], and size of involved vessels in 471 surgically resected PDACs were evaluated with all available hematoxylin and eosin (H&E)-stained slides.

RESULTS

Venous invasion was observed in 319 cases (67.7%) and was more frequently associated with increased tumor size, extrapancreatic extension, resection margin involvement, diffuse tumor distribution, lymph node metastasis, and perineural invasion (all Ps < .05). High frequency (≥3 foci) of venous invasion was associated with shorter overall survival both in the entire group and in the early stage subgroup (stage I; all Ps < .05). Multivariate analysis indicated that a high frequency (≥3 foci) of venous invasion, large tumor size (>4 cm), higher histologic grade, and lymph node metastasis, were independent prognostic factors of worse overall survival (all Ps < .05).

CONCLUSION

Precise evaluation of venous invasion status, including foci number of invasion, can provide additional prognostic information for patients undergoing surgical resection of PDAC, especially for those with early disease stage.

Autoimmune pancreatitis: an update

OBJECTIVE

Since the time of inception of autoimmune pancreatitis (AIP), our knowledge of autoimmune pancreatitis has expanded significantly. The aim of this review is to provide an update on clinical manifestations, diagnosis, imaging features, and treatment of AIP.

BACKGROUND AND CLINICAL SIGNIFICANCE

Type 1 AIP is the pancreatic manifestation of IgG4-related systemic disease, which can be diagnosed using a combination of clinical, histopathological, pancreatic imaging findings in conjunction with manifestation in other organs, as well of responsiveness to steroid treatment. It is vital to differentiate AIP from pancreatic cancer since both can mimic each other clinically and radiologically. Type 2 AIP is a rare but distinct subtype of AIP which occurs mostly in the younger patient.

CONCLUSION

AIP is steroid-responsive chronic pancreatitis with distinct manifestations on imaging.

Diffuse Pancreatic Cancer Mimicking Autoimmune Pancreatitis

The characteristic finding of sausage-shaped pancreas or capsule-like rim facilitates the diagnosis of autoimmune pancreatitis. We herein report a case of a 67-year-old man showing a sausage-shaped, enlarged pancreas with a capsule-like rim on computed tomography. Furthermore, endoscopic retrograde cholangiopancreatography demonstrated diffuse narrowing of the main pancreatic duct, in addition to stenosis of the lower bile duct. Finally, we were able to diagnose pancreatic cancer in this patient by an endoscopic ultrasound-guided fine-needle aspiration biopsy following peroral cholangioscopy and bile cytology. This report emphasizes the significance of pathological confirmation before starting treatment, even in cases with diffuse pancreatic enlargement.

Pancreatic duct "Icicle sign" on MRI for distinguishing autoimmune pancreatitis from pancreatic ductal adenocarcinoma in the proximal pancreas

OBJECTIVE

To determine reliable MRI features of autoimmune pancreatitis (AIP) in the proximal pancreas that could allow its differentiation from pancreatic ductal adenocarcinoma (PDAC).

METHODS

Twenty-three patients with AIP and 61 patients with PDAC in the proximal pancreas underwent MRI. Two observers analyzed MRI for lesion morphology, hypointensity degree on T1-weighted images, enhancement pattern during dynamic phases, capsule-like rim, presence of cysts and duct penetrating sign, morphology of bile duct, and icicle appearance and tortuosity of the upstream pancreatic duct. Sensitivity and specificity for the diagnosis of AIP were calculated for each category or combined.

RESULTS

When isointensity on the portal and late phase of MRI and/or the icicle sign of pancreatic duct are applied, 100 % sensitivity for the diagnosis of AIP in the proximal pancreas was achieved. Applying both mild T1 hypointensity similar to the spleen and the icicle sign enabled 100 % specificity for the diagnosis of AIP by differentiating it from PDAC.

CONCLUSION

The combination of the icicle sign in the upstream pancreatic duct and mild T1 hypointensity or isointensity on portal and late phase of dynamic MRI could be reliable MR features for the diagnosis of AIP in the proximal pancreas by allowing its differentiation from PDAC.

KEY POINTS

• The icicle sign of the pancreatic duct is useful for diagnosing AIP. • Mild T1 hypointensity similar to the spleen is useful for diagnosing AIP. • Isointensity on portal and late phases MRI is useful for diagnosing AIP.

Magnetic resonance cholangiopancreatography for the diagnostic evaluation of autoimmune pancreatitis

OBJECTIVE

The aim of this study was to determine the role of magnetic resonance cholangiopancreatography (MRCP) for diagnosing autoimmune pancreatitis (AIP) and the accuracy of MRCP in depicting the main pancreatic duct (MPD) morphology of AIP using endoscopic retrograde cholangiopancreatography (ERCP) as the reference standard.

METHODS

Thirty-eight AIP patients, 40 pancreatic cancer patients, and 40 patients with normal pancreas were included. MRCP was interpreted in association with cross-sectional magnetic resonance images regarding MPD morphology, pancreatic parenchyma, and extrapancreatic abnormalities. Main pancreatic duct was interpreted as narrowed when a narrowed-appearing segment on MRCP was associated with upstream dilatation or pancreatic parenchymal abnormalities in the same location.

RESULTS

Accuracy of MRCP for depicting MPD morphology of AIP (64.7% [22/34]) was lower than those for pancreatic cancer (88.5% [23/26]) (P = 0.041) or normal pancreas (100% [40/40]) (P < 0.0005). The inaccuracy in AIP was primarily (10/12) due to overestimation of MPD narrowing. Of various differing MRCP findings between AIP and pancreatic cancer, multiple MPD narrowing (AIP vs cancer, 27/38 vs 0/40) and upstream MPD dilatation greater than 5 mm in diameter (AIP vs cancer, 0/38 vs 10/40) could exclude pancreatic cancer and AIP, respectively.

CONCLUSIONS

MRCP cannot replace ERCP for the diagnostic evaluation of AIP but may deserve to be used when ERCP has been unsuccessful or is difficult to perform.

Imaging findings in a case of mixed acinar-endocrine carcinoma of the pancreas

Mixed acinar-endocrine carcinoma (MAEC) of the pancreas is extremely uncommon. We report here a rare case of MAEC of the pancreas presenting as watery diarrhea. This is the first report in the English-language literature that describes the imaging findings of MAEC of the pancreas, including computed tomography (CT), magnetic resonance (MR) imaging, and MR cholangiopancreatography features.