Autoimmune pancreatitis: Multimodality non-invasive imaging diagnosis

Autoimmune pancreatitis type 2 (idiopathic duct-centric pancreatitis): A comprehensive review

Autoimmune pancreatitis (AIP) is an uncommon fibro-inflammatory disorder precipitated by autoimmune/inflammatory reactions. Currently, there are two clinical subtypes of AIP (type 1 [AIP-1] and type 2 [AIP-2]) that correspond to two histologic descriptors (lymphoplasmacytic sclerosing pancreatitis and idiopathic duct-centric pancreatitis, respectively). While our understanding of AIP-1 has evolved considerably over the years, little is known about AIP-2 due to its rarity, often leading to misdiagnosis, delayed treatment, and even unnecessary surgical resection. Compared to AIP-1, AIP-2 exhibits distinct clinical and histologic features. Because AIP-2 is a pancreas-restricted disease without a specific serum marker, the evaluation of histologic features (e.g., granulocytic epithelial lesions) is essential for an accurate diagnosis. Patients with AIP-2 respond well to glucocorticoids, with anti-tumor necrosis factor-alpha antibodies as a promising alternative therapy. The prognosis of AIP-2 is generally favorable and relapse is uncommon. Here, we provide an overview of our current knowledge on the clinical features, diagnosis, therapeutic regimens, prognosis, and putative mechanisms underlying AIP-2. Notably, the diagnostic differentiation between AIP-2, especially the mass-forming/focal type, and pancreatic cancer is important, but challenging. In this regard, endoscopic ultrasound-guided core biopsy has a key role, but novel diagnostic markers and modalities are clearly needed.

Anatomic and Functional Imaging of Immunoglobulin G4-related Disease and Its Mimics

Immunoglobulin G4 (IgG4)-related disease (IgG4-RD) is an immune-mediated fibrosclerosing disease with tumefactive lesions infiltrated by IgG4-positive plasma cells. Initially described as autoimmune pancreatitis, IgG4-RD is now recognized as a discrete entity and is found to affect virtually any organ in the body. Common extrapancreatic sites include the biliary tree, salivary glands, periorbital tissue, lungs, kidneys, lymph nodes, aorta, retroperitoneum, and thyroid gland. Diagnosis-which relies on histopathologic, serologic, and radiologic features-can be challenging with the disease underdiagnosed, as IgG4-RD often mimics malignancy, infectious processes, or other immune-mediated conditions. Patients may present with signs of compression of nearby structures due to mass effect or with organ failure when the disease is left untreated. The clinical course is complex, with single- or multiorgan involvement and metachronous or synchronous occurrence of lesions. IgG4-RD responds well to glucocorticoid therapy, disease-modifying antirheumatic drugs, and B-cell-depleting biologic agents; prompt diagnosis is important to avoid delay in treatment and unnecessary pharmacologic or surgical intervention. While imaging features may not be specific for IgG4-RD, functional whole-body imaging with fluorine 18-fluorodeoxyglucose PET/CT is a useful adjunct for localizing extrapancreatic sites for biopsy, monitoring therapeutic response, and demonstrating disease relapse. The authors describe the pancreatic and extrapancreatic sites of involvement in IgG4-RD, with imaging features and patterns to aid in distinguishing IgG4-RD from its mimics through a multimodality approach with emphasis on functional imaging evaluation. ^©RSNA, 2023 Quiz questions in the supplemental material and the slide presentation from the RSNA Annual Meeting are available for this article.

CT Radiomics Features in Differentiation of Focal-Type Autoimmune Pancreatitis from Pancreatic Ductal Adenocarcinoma: A Propensity Score Analysis

PURPOSE

To evaluate the diagnostic performance of the radiomics score (rad-score) for differentiating focal-type autoimmune pancreatitis (fAIP) from pancreatic ductal adenocarcinoma (PDAC).

METHODS

This retrospective review included 42 consecutive patients with fAIP diagnosed according to the International Consensus Diagnostic Criteria between January 2011 and December 2018. Furthermore, 334 consecutive patients with PDAC confirmed by pathology were also reviewed during the same period. Patients with PDAC and fAIP were matched via propensity score matching (PSM). All patients underwent multidetector computed tomography (MDCT). For each patient, 1409 radiomics features of the portal phase were extracted and reduced using the least absolute shrinkage and selection operator (LASSO) logistic regression algorithm. The portal rad-score performance was assessed based on its discriminative ability.

RESULTS

After PSM, we matched 55 patients with PDAC to 42 patients with fAIP, based on clinical and CT characteristics (e.g., patient age, sex, body mass index, location, size, enhanced mode). A rad-score for discriminating fAIP from PDAC, which contained four CT derived radiomic features, was developed (area under the curve = 0.97). The sensitivity, specificity, and accuracy of the radiomics model were 95.24%, 92.73% and 0.94, respectively.

CONCLUSION

The portal rad-score can accurately and noninvasively differentiate fAIP from PDAC.

Persistent enlargement of the pancreatic gland after glucocorticoid therapy increases the risk of relapse in IgG4-related autoimmune pancreatitis

OBJECTIVES

This study aims to clarify the relationship between the changes of pancreatic size after glucocorticoid (GC) therapy and relapse in IgG4-related autoimmune pancreatitis (AIP).

METHODS

We prospectively enrolled 205 newly diagnosed IgG4-related AIP patients. 145 patients were followed up for more than 3 years. These patients were divided into three groups according to the changes of pancreatic size after treatment of 6 months: pancreatic swelling, normal size, and pancreatic atrophy. Baseline clinical and laboratory parameters were compared among three groups. Kaplan-Meier survival analysis was performed in the 134 patients based on GC therapy. Besides, Cox regression analysis and logistic regression analysis were performed to identify risk factors associated with relapse and the potential variables affecting changes of pancreatic size after treatment.

RESULTS

Age at diagnosis, white blood cell count, and serum IgG1 level at baseline were significantly different among the three groups. After treatment of 6 months, the pancreas of most patients (n = 81, 55.9%) could return to normal size, while persistent pancreatic swelling was found in 24.1% patients (n = 35), and atrophy was observed in 20.0% of the patients (n = 29). Kaplan-Meier survival analysis presented patients with pancreatic swelling after 6 months of GC therapy were more likely to relapse in the follow-up of 3 years. Persistent pancreatic swelling after treatment and salivary gland involvement at baseline were independent risk variables associated with relapse in IgG4-related AIP patients, while GC-based therapy was a protective factor of relapse. Logistic regression analysis revealed that older age at diagnosis was associated with pancreatic atrophy and higher baseline serum IgG1 level was associated with pancreatic swelling after treatment of 6 months.

CONCLUSIONS

Patients with persistent pancreatic swelling after GC-based therapy of 6 months were more likely to relapse in the follow-up of 3 years. Older age at diagnosis and higher baseline serum IgG1 level were potential variables associated with pancreatic atrophy or swelling after treatment of 6 months. Key Points • Patients with persistent pancreatic swelling after glucocorticoid-based therapy were more likely to relapse in IgG4-related autoimmune pancreatitis. • Older age at diagnosis was associated with pancreatic atrophy after glucocorticoid-based therapy. • Higher baseline serum IgG1 level was associated pancreatic swelling after glucocorticoid-based therapy.

Solid pancreatic masses in children: A review of current evidence and clinical challenges

Pancreatic tumors in children are infrequently encountered in clinical practice. Their non-specific clinical presentation and overlapping imaging characteristics often make an accurate preoperative diagnosis difficult. Tumors are categorized as epithelial or non-epithelial, with epithelial tumors further classified as tumors of the exocrine or endocrine pancreas. Although both are tumors of the exocrine pancreas, solid pseudopapillary neoplasm is the most prevalent solid pancreatic tumor in children, while pancreatoblastoma is the most common malignant tumor. Insulinoma is the most common pediatric pancreatic tumor of the endocrine pancreas. Malignant tumors require a complete, often radical, surgical resection. However, pancreatic parenchyma-sparing surgical procedures are utilized for benign tumors and low-grade malignancy to preserve gland function. This review will discuss the epidemiology, pathophysiology, clinical and diagnostic characteristics, and management options associated with both common and rare solid pancreatic masses in children. We will also discuss current challenges encountered in their evaluation and treatment.

Use of MRI signal intensity ratio to differentiate between autoimmune pancreatitis and pancreatic ductal adenocarcinoma

AIM

To evaluate the accuracy of the lesion-to-erector spinae signal intensity ratio (SIR) on magnetic resonance imaging (MRI) for distinguishing autoimmune pancreatitis (AIP) from pancreatic ductal adenocarcinoma (PDA).

MATERIALS AND METHODS

The MRI data of 21 patients with AIP and 27 patients with PDA were analysed retrospectively, and the signal intensity in pancreatic lesions and erector spinae muscles at the same level on T2-weighted imaging (T2WI), arterial phase (AP) imaging, and delayed phase (DP) imaging was measured for calculation of SIRs.

RESULTS

The mean SIRs of the pancreatic lesions and erector spinae from T2WI, AP, and DP images of AIP patients were 0.96, 1.27, and 1.42, respectively, while those of PDA patients were 1.35, 0.80, and 0.91, respectively. The differences in the SIRs between the AIP and PDA groups were statistically significant (p<0.001), with corresponding area under curve (AUC) values of 0.925, 0.906, and 0.961, respectively. The optimal cut-off values for the SIRs on T2WI, AP and DP images were 1.21, 1.01, and 1.08, respectively. SIR values < 1.21 on T2WI, >1.01 on AP imaging, and >1.08 on DP imaging identified AIP with sensitivities of 85.7%, 90.5%, and 90.5%, respectively, and specificities of 81.5%, 74.6%, and 81.5%, respectively. The AUC values for SIRs did not differ significantly between T2WI and DP imaging or AP and DP imaging (Z = 0.778, p=0.436; Z = 1.279, p=0.201).

CONCLUSION

The SIRs of pancreatic lesions and erector spinae on T2WI, AP, and DP images can be used to differentiate AIP from PDA.

Autoimmune pancreatitis presenting as a pancreatic head mass

The diagnosis of autoimmune pancreatitis (AIP) is often difficult as the main differential diagnosis is pancreatic head adenocarcinoma. Some clinical, radiological, serological and histological criteria help in guiding the diagnosis. The serum gamma-globulin IgG4 dosage is the most sensitive and specific marker. The shape of the ductal stenosis in AIP is characteristic. The treatment is based on corticosteroids. We report the case of a 53-year-old woman, presenting with pancreatic head mass mimicking an adenocarcinoma.

Benign vs malignant pancreatic lesions: Molecular insights to an ongoing debate

Several benign conditions such as chronic pancreatitis, autoimmune pancreatitis, and paraduodenal pancreatitis can present as mass lesions and may mimic pancreatic ductal adenocarcinoma (PDAC) clinically and radiologically. Thorough histologic examination with attention to certain morphologic features can assist in deciphering neoplastic from reactive, however small biopsies often remain a challenge. Variable histologic patterns in conventional PDAC may also confound the diagnosis of PDAC. Uncommon subtypes of pancreatic carcinoma such as adenosquamous and squamous cell carcinoma, colloid carcinoma, medullary carcinoma, hepatoid carcinoma and signet ring cell carcinoma necessitate excluding metastasis from other sites prior to rendering the diagnosis of pancreatic carcinoma. The use of immunohistochemical staining and molecular markers can aid in separating benign from malignant and PDAC from metastasis. PDAC expresses a few non-specific epithelial and mucin immunomarkers such as CK7, CK19, MUC1, MUC4 and MUC5AC. However, the only immunohistochemical marker that is specific for PDAC in the right clinical context is SMAD4. Loss of SMAD4 within atypical glands and ducts supports the diagnosis of PDAC in a limited sample. Unfortunately, this finding is seen only in 50% of PDAC cases. The identification of certain mutations can help support a diagnosis of PDAC when benign conditions are in the differential. At the molecular level, KRAS oncogene mutations are seen in approximately 93% of PDACs. Subsequent neoplastic progression is driven by additional mutations of tumor suppressor genes, such as CDKN2A, TP53, and SMAD4. Molecular markers can also provide an insight to the prognosis. For instance, the loss of SMAD4 is associated with a poor outcome whereas mutations in MLL, MLL2, MLL3, and ARID1A are associated with improved survival.

Mass Mimicking Autoimmune Pancreatitis—A Report of Two Cases and Review of Literature

Autoimmune pancreatitis (AIP) consists of two clinically histologically distinct forms (type I and II) of chronic pancreatitis that are histologically different. These forms of AIP classically respond to oral steroids. The focal form of AIP resembles pancreatic carcinoma both clinically and radiologically and it is of utmost importance to make an early correct diagnosis between these two diseases in order to identify the optimal therapeutic strategy and to avoid unnecessary laparotomy or pancreatic resection in AIP patients. Here we report focal forms of type I and II AIP with clinical and imaging features closely mimicking pancreatic carcinoma.

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.

Pancreas Solid Tumors

Solid tumors of the pancreas encompass a variety of diagnoses with treatments ranging from observation to major abdominal surgery. Pancreatic ductal adenocarcinoma remains one of the most common and most lethal of these differential of diagnoses and requires a multimodality approach through a multidisciplinary team of specialists. This article reviews the classification, clinical presentation, and workup in differentiating solid tumors of the pancreas and serves as an additional tool for general surgeons faced with such a clinical finding, from a surgical oncology perspective.

Differentiating autoimmune pancreatitis from pancreatic ductal adenocarcinoma with CT radiomics features

PURPOSE

The purpose of this study was to determine whether computed tomography (CT)-based machine learning of radiomics features could help distinguish autoimmune pancreatitis (AIP) from pancreatic ductal adenocarcinoma (PDAC).

MATERIALS AND METHODS

Eighty-nine patients with AIP (65 men, 24 women; mean age, 59.7±13.9 [SD] years; range: 21-83 years) and 93 patients with PDAC (68 men, 25 women; mean age, 60.1±12.3 [SD] years; range: 36-86 years) were retrospectively included. All patients had dedicated dual-phase pancreatic protocol CT between 2004 and 2018. Thin-slice images (0.75/0.5mm thickness/increment) were compared with thick-slices images (3 or 5mm thickness/increment). Pancreatic regions involved by PDAC or AIP (areas of enlargement, altered enhancement, effacement of pancreatic duct) as well as uninvolved parenchyma were segmented as three-dimensional volumes. Four hundred and thirty-one radiomics features were extracted and a random forest was used to distinguish AIP from PDAC. CT data of 60 AIP and 60 PDAC patients were used for training and those of 29 AIP and 33 PDAC independent patients were used for testing.

RESULTS

The pancreas was diffusely involved in 37 (37/89; 41.6%) patients with AIP and not diffusely in 52 (52/89; 58.4%) patients. Using machine learning, 95.2% (59/62; 95% confidence interval [CI]: 89.8-100%), 83.9% (52:67; 95% CI: 74.7-93.0%) and 77.4% (48/62; 95% CI: 67.0-87.8%) of the 62 test patients were correctly classified as either having PDAC or AIP with thin-slice venous phase, thin-slice arterial phase, and thick-slice venous phase CT, respectively. Three of the 29 patients with AIP (3/29; 10.3%) were incorrectly classified as having PDAC but all 33 patients with PDAC (33/33; 100%) were correctly classified with thin-slice venous phase with 89.7% sensitivity (26/29; 95% CI: 78.6-100%) and 100% specificity (33/33; 95% CI: 93-100%) for the diagnosis of AIP, 95.2% accuracy (59/62; 95% CI: 89.8-100%) and area under the curve of 0.975 (95% CI: 0.936-1.0).

CONCLUSIONS

Radiomic features help differentiate AIP from PDAC with an overall accuracy of 95.2%.

Type 1 and Type 2 Autoimmune Pancreatitis: Distinctive Clinical and Pathological Features, But Are There Any Differences at Magnetic Resonance? Experience From a Referral Center

OBJECTIVES

This study aimed to evaluate magnetic resonance imaging findings of autoimmune pancreatitis (AIP) and to find radiological patterns that could differentiate type 1 and type 2 AIP.

METHODS

Eighty-four patients with diagnosis of AIP were enrolled. Image analysis included pancreatic signal intensity abnormalities, enhancement pattern, extrapancreatic involvement, and main pancreatic duct alterations.

RESULTS

Pancreatic parenchyma resulted in hypointensity on T1-weighted images in 65 (98.5%) of 66 cases in type 1 and in 17 (94.5%) of 18 in type 2 (P > 0.05) and in hyperintensity on T2-weighted images in 41 (62%) of 66 and in 15 (83.4%) of 18, respectively (P > 0.05). Lesions were hypovascular in 64 (97%) of 66 cases in type 1 and in 16 (88.9%) of 18 in type 2 with delayed contrast retention in 56 (84.8%) of 66 and in 17 (94.5%) of 18, respectively (P > 0.05). Autoimmune cholangitis was found in 29 (43.9%) of 66 patients with type 1 and in 3 (16.7%) of 18 with type 2 (P = 0.02); renal involvement was observed in 20 (30.3%) of 66 and 1 (5.5%) of 18, respectively (P = 0.02). Both subtypes presented with multiple stenoses (P > 0.05). Dilation of upstream duct was more frequent in type 1 (P = 0.02).

CONCLUSIONS

Magnetic resonance imaging is useful in detecting extrapancreatic involvement, typically seen in type 1. Dilation of the upstream duct suggests type 1 AIP.

Imaging in Autoimmune Pancreatitis and Immunoglobulin G4-Related Disease of the Abdomen

Autoimmune pancreatitis (AIP) is steroid-responsive fibroinflammatory disorder of the pancreas. There are 2 distinct subtypes of AIP, types 1 and 2. Type 1 is associated with systemic immunoglobulin (Ig)G4 disease and may affect multiple organs in the body. Type 2 is confined to the pancreas and shows an association with ulcerative colitis. This article describes the imaging findings of AIP and IgG4 disease in the liver, bile ducts, kidneys, and the retroperitoneal regions. The imaging differentiation of AIP from pancreas cancer is discussed.

A Rare Multifocal Pattern of Type 2 Autoimmune Pancreatitis with Negative IgG4: A Potential Diagnostic Pitfall That May Mimic Multifocal Pancreatic Adenocarcinoma

Autoimmune pancreatitis (AIP) is an increasingly recognized form of acute pancreatitis characterized by obstructive jaundice with a rapid and dramatic treatment response to steroid therapy. Recently, AIP has been divided into two distinct phenotypes: lymphoplasmocytic sclerosing pancreatitis AIP (type 1) and idiopathic duct-centric pancreatitis AIP (type 2); each of which have their own distinct demographics, diagnostic criteria, and histopathological features. We report, to the best of our knowledge, the first case of a multifocal pattern of type 2 AIP characterized with both CT and MR imaging. This rare imaging pattern of AIP may mimic the appearance of more worrisome malignant etiologies such as multifocal pancreatic adenocarcinoma or lymphoma, with overlapping imaging characteristics potentially complicating or delaying diagnosis. Therefore, recognition of this atypical pattern of AIP and avoidance of this potential diagnostic pitfall is crucial.

Autoimmune Pancreatitis and Inflammatory Bowel Disease: An Updated Review

Autoimmune pancreatitis (AIP) occurring in association with inflammatory bowel disease (IBD) is rather rare and carries a worse prognosis and greater disease severity compared with IBD alone. Although it is an infrequently documented association, progress over the last 20 years has led to better understanding of the association between AIP and IBD. IBD has a stronger association with type 2 than with type 1 AIP. Clinical and histologic features of AIP-IBD more often reveal features of type 2 AIP. Imaging is not helpful in facilitating the diagnosis of AIP and IBD. Similarly, attempts to identify a serological marker have not yielded better result. A proposed lymphocyte homing mechanism provides some insight into the mechanism of pathogenesis. This review represents an update of our current knowledge of the association between AIP and IBD.

CT and MRI of Rare Extraintestinal Manifestations of Inflammatory Bowel Disease in Children and Adolescents

Inflammatory bowel disease (IBD) is associated with a spectrum of extraintestinal manifestations (EIMs) affecting many organ systems. EIMs can occur in more than 40% of patients with IBD and are associated with significant morbidity. They occur at any time point in the course of disease, often during an active phase of bowel inflammation, but sometimes preceding bowel disease. Prompt recognition of EIMs enables timely and more effective therapy. Physicians who image patients with IBD should be aware of the myriad extraintestinal conditions that may be detected on imaging studies, both within and outside of the abdomen, as they may predate the diagnosis of IBD. Cross-sectional imaging of unusual conditions associated with IBD will be presented, including pathology in the hepatobiliary, pancreatic, genitourinary, musculoskeletal, mucocutaneous, vascular, neurologic, and pulmonary systems.