Localization of the most severely dysplastic/invasive lesions and mucin phenotypes in intraductal papillary mucinous neoplasm of the pancreas

Important radiological and clinicopathological risk factors for the recurrence of intraductal papillary mucinous neoplasms after surgical resection

OBJECTIVES

To assess significant radiological and clinicopathological risk factors for post-surgery recurrence in patients with intraductal papillary mucinous neoplasm (IPMN).

MATERIALS AND METHODS

Patients with IPMNs who underwent surgery from 2011 to 2021 at a single center were retrospectively included. Two reviewers evaluated CT findings according to international guidelines. Clinicopathological data were collected from medical records and surgical pathology reports. Patients were monitored for recurrence with contrast-enhanced CT or MRI up to 2023. Univariable Cox regression analysis included potential risk factors: all high-risk stigmata and worrisome features in the international guidelines, age, sex, tumor location, type, carcinoembryonic antigen, surgery type, postsurgical residual cyst, adjuvant treatment, pathologic grade, type, size, margin status, lymph node metastasis, gland type, and pancreatic intraepithelial neoplasia. Variables with p < 0.2 were included in multivariate analysis.

RESULTS

Among 332 patients (mean age, 66.3 ± 9.0 years; 212 men), recurrence occurred in 39 (11.7%) over a median follow-up of 3.2 years (range: 0.1-12.3 years). Two- and five-year recurrence-free survival rates were 91.2% and 86.4%, respectively. Significant radiological risk factors included enhancing mural nodule (EMN) presence (hazard ratio [HR] 5.088, p = 0.007) and lymphadenopathy (HR 2.837, p = 0.01). Associated invasive carcinoma (HR 25.030), lymph node metastasis (HR 27.562), adjuvant treatment (HR 0.203), and history of pancreatitis (HR 2.608) were also significant. Most imaging features showed moderate to excellent interobserver agreement, except for thickened/enhancing cyst walls (κ, 0.25).

CONCLUSION

The presence of EMNs and lymphadenopathy, along with several clinicopathologic factors, were significantly associated with IPMN recurrence.

KEY POINTS

Question Understanding postoperative recurrence risk in IPMN patients is crucial for determining surveillance strategies; however, research on radiologic risk factors remains limited. Findings The presence of EMNs and lymphadenopathy were identified as significant radiologic risk factors for the postoperative recurrence of IPMN, along with clinicopathologic factors. Clinical relevance IPMN recurrence is significantly associated with imaging findings like EMNs and lymphadenopathy, as well as clinical and pathologic factors. It can guide the development of tailored postoperative surveillance strategies for IPMN patients in further studies.

Mural nodules and prevalence of high-grade dysplasia in branch duct intraductal papillary mucinous neoplasm of the pancreas undergoing resection

BACKGROUND

A mural module (MN) within a branch-duct intraductal papillary mucinous neoplasm (BD-IPMN) could be a potential target for local treatment. The main aim was to describe the location of the highest grade of dysplasia relative to the mural module to assess the relevance of local treatment.

METHODS

Observational study of patients who underwent a pancreatic resection for suspected high-risk IPMN because of a mural module within a BD-IPMN (2012-2022). All patients had preoperative imaging confirming the enhancing mural module. The mural module was considered as a theoretical appropriate target for local destruction if no cancer or high-grade dysplasia (HGD) was described elsewhere than in the mural module.

RESULTS

Eighty-two patients (male: 44 (54%); mean age: 65 ± 9.2 years) were included. The mean size of BD-IPMN containing the mural module was 32 ± 14.8 mm. The mural module mean diameter was 10.5 ± 5.6 mm, and the main pancreatic duct (MPD) mean diameter was 5.2 ± 3.6 mm. Six patients presented invasive carcinoma (7%), 37 had HGD (45%), and 39 (48%) had exclusively low-grade dysplasia. The mural module was dysplastic in 70 cases (85%). The mural module was considered a relevant target for local ablation in 45 patients (55%), whereas 37 patients (45%) had HGD/invasive carcinoma distant from the mural module. HGD was exclusively present in the mural module in 6/82 patients (7%). Factors independently associated with 'relevant indication for local treatment' were female gender (P = 0.004; OR = 5.2, 95% c.i. 1.7 to 15.9) and MPD < 5 mm (P < 0.0001; OR = 8.6, 95% c.i. 2.7 to 26.8).

CONCLUSION

In resected pancreata, BD-IPMN mural modules are associated with HGD distant from the mural module almost half of cases. The findings question the safety of local treatment, supporting pancreatectomy as the best approach.

Intraductal Pancreatic Mucinous Neoplasms: A Tumor-Biology Based Approach for Risk Stratification

Pancreatic ductal adenocarcinoma is one of the most lethal human cancers. Its precursor lesions include pancreatic intra-epithelial neoplasia, mucinous cystic neoplasm, and intraductal papillary mucinous neoplasm (IPMN). IPMNs usually present as an incidental finding at imaging in 2.6% of the population and, according to the degree of dysplasia, they are classified as low- or high-grade lesions. Since the risk of malignant transformation is not accurately predictable, the management of these lesions is based on morphological and clinical parameters, such as presence of mural nodule, main pancreatic duct dilation, presence of symptoms, or high-grade dysplasia. Although the main genetic alterations associated to IPMNs have been elucidated, they are still not helpful for disease risk stratification. The growing body of genomic and epigenomic studies along with the more recent development of organotypic cultures provide the opportunity to improve our understanding of the malignant transformation process, which will likely deliver biomarkers to help discriminate between low- and high-risk lesions. Recent insights on the topic are herein summarized.

Metachronous intraductal papillary mucinous neoplasms disseminate via the pancreatic duct following resection

Metachronous development of intraductal papillary mucinous neoplasms in the remnant pancreas following resection is a significant clinical burden. Our aim was to characterize the clinicopathological and molecular features of the patients with metachronous tumor development to identify predictive factors and the possible route(s) of dissemination. Seventy-four patients who underwent resection of intraductal papillary mucinous neoplasms with no invasive compartment or associated carcinoma were retrospectively analyzed. In patients with metachronous tumor development, targeted sequencing of 18 genes associated with pancreatic tumorigenesis and immunohistochemical detection of four proteins (p53, SMAD4, p16, and β-catenin) were performed on both primary and metachronous tumors. The distributions of microscopic neoplastic lesions were examined at surgical margins and in apparently normal tissue apart from the primary tumor. During the median follow-up period of 52 months, 9 patients (12%) developed metachronous tumors in the remnant pancreas. Primary tumors located in the body/tail of the pancreas (odds ratio, 15; 95% confidence interval, 1.6-131) and of the pancreatobiliary type (odds ratio, 6.1; 95% confidence interval, 1.1-35.7) were identified as significant risk factors for subsequent metachronous tumor development. Eight of the nine patients shared molecular aberrations between their primary and metachronous tumors, suggesting migrations from the primary tumor to the pancreatic duct as the cause of metachronous tumor development. Our data suggest that these post-resection metachronous tumors develop by skip dissemination of the primary tumor, potentially via the pancreatic duct. The development of strategies to better predict and prevent this form of tumor progression is necessary.

Pathways of Progression From Intraductal Papillary Mucinous Neoplasm to Pancreatic Ductal Adenocarcinoma Based on Molecular Features

BACKGROUND & AIMS

Intraductal papillary mucinous neoplasms (IPMNs) are regarded as precursors of pancreatic ductal adenocarcinomas (PDAs), but little is known about the mechanism of progression. This makes it challenging to assess cancer risk in patients with IPMNs. We investigated associations of IPMNs with concurrent PDAs by genetic and histologic analyses.

METHODS

We obtained 30 pancreatic tissues with concurrent PDAs and IPMNs, and 168 lesions, including incipient foci, were mapped, microdissected, and analyzed for mutations in 18 pancreatic cancer-associated genes and expression of tumor suppressors.

RESULTS

We determined the clonal relatedness of lesions, based on driver mutations shared by PDAs and concurrent IPMNs, and classified the lesions into 3 subtypes. Twelve PDAs contained driver mutations shared by all concurrent IPMNs, which we called the sequential subtype. This subset was characterized by less diversity in incipient foci with frequent GNAS mutations. Eleven PDAs contained some driver mutations that were shared with concurrent IPMNs, which we called the branch-off subtype. In this subtype, PDAs and IPMNs had identical KRAS mutations but different GNAS mutations, although the lesions were adjacent. Whole-exome sequencing and methylation analysis of these lesions indicated clonal origin with later divergence. Ten PDAs had driver mutations not found in concurrent IPMNs, called the de novo subtype. Expression profiles of TP53 and SMAD4 increased our ability to differentiate these subtypes compared with sequencing data alone. The branch-off and de novo subtypes had substantial heterogeneity among early clones, such as differences in KRAS mutations. Patients with PDAs of the branch-off subtype had a longer times of disease-free survival than patients with PDAs of the de novo or the sequential subtypes.

CONCLUSIONS

Detailed histologic and genetic analysis of PDAs and concurrent IPMNs identified 3 different pathways by which IPMNs progress to PDAs-we call these the sequential, branch-off, and de novo subtypes. Subtypes might be associated with clinical and pathologic features and be used to select surveillance programs for patients with IPMNs.

Systematic review, meta-analysis, and a high-volume center experience supporting the new role of mural nodules proposed by the updated 2017 international guidelines on IPMN of the pancreas

BACKGROUND

Mural nodules (MNs) have a predominant role in the 2016 revision of the international guidelines on intraductal papillary mucinous neoplasms (IPMN) of the pancreas. The aim of this study was to evaluate MNs as predictors of invasive cancer (iCa) or high-grade dysplasia (HGD) in IPMNs and to investigate the role of MN size in risk prediction.

METHODS

A PRISMA-compliant systematic review of the literature and meta-analysis on selected studies were conducted. The random effect model was adopted, and the pooled SMD (standardized mean difference) obtained. The surgical series of IPMNs at a single high-volume institution was reviewed.

RESULTS

This review included 70 studies and 2297 resected IPMNs. MNs have a positive predictive value for malignancy of 62.2%. The meta-analysis suggested that MN size has a considerable effect on predicting IPMNs with both iCa or HGD with a mean SMD of 0.79. All studies included in the meta-analysis used contrast-enhanced endosonography (CE-EUS) to assess MNs. Due to the heterogeneity of the proposed thresholds, no reliable MN size cut-off was identified. Of 317 IPMNs resected at our institution, 102 (32.1%) had a preoperative diagnosis of MN. Multivariate analysis showed that MN is the only independent predictor of iCa and HGD for all types of IPMNs.

CONCLUSION

MNs are reliable predictors of iCa and HGD in IPMNs as proposed by the 2016 IAP guidelines. CE-EUS seems to be the best tool for characterizing size and has the best accuracy for predicting malignancy. Further studies should determine potential MN dimensional cut-offs.

Diversity of Precursor Lesions For Pancreatic Cancer: The Genetics and Biology of Intraductal Papillary Mucinous Neoplasm

Pancreatic ductal adenocarcinoma (PDA), one of the most lethal cancers worldwide, is associated with two main types of morphologically distinct precursors—pancreatic intraepithelial neoplasia (PanIN) and intraductal papillary mucinous neoplasm (IPMN). Although the progression of PanIN into invasive cancer has been well characterized, there remains an urgent need to understand the biology of IPMNs, which are larger radiographically detectable cystic tumors. IPMNs comprise a number of subtypes with heterogeneous histopathologic and clinical features. Although frequently remaining benign, a significant proportion exhibits malignant progression. Unfortunately, there are presently no accurate prognosticators for assessing cancer risk in individuals with IPMN. Moreover, the fundamental mechanisms differentiating PanIN and IPMN remain largely obscure, as do those that distinguish IPMN subtypes. Recent studies, however, have identified distinct genetic profiles between PanIN and IPMN, providing a framework to better understand the diversity of the precursors for PDA. Here, we review the clinical, biological, and genetic properties of IPMN and discuss various models for progression of these tumors to invasive PDA.

Tracking the Clonal Evolution of Adenosquamous Carcinoma, a Rare Variant of Intraductal Papillary Mucinous Neoplasm of the Pancreas

Adenosquamous carcinoma (ASC) is an uncommon variant of pancreatic neoplasm. We sought to trace the mode of tumor progression using specimens of ASC associated with intraductal papillary mucinous neoplasm (IPMN) of the pancreas. A resected specimen of the primary pancreatic ASC, developed in a 72-year-old man, was subjected to mutation profiling using amplicon-targeted sequencing and digital polymerase chain reaction. DNA was isolated from each histological compartment including noninvasive IPMN, squamous cell carcinoma (SCC), and adenocarcinoma (AC). Histologically, an IPMN with a large mural nodule was identified. The invasive tumor predominantly consisted of SCC, and a smaller AC was found around the lesion. Squamous metaplasias were sporadically distributed within benign IPMNs. Mutation alleles KRAS and GNAS were identified in all specimens of IPMN including the areas of squamous metaplasia. In addition, these mutations were found in SCC and AC. Clear transition from flat/low-papillary IPMN to SCC indicated a potent invasion front, and the SCC compartment was genetically unique, because the area has a higher frequency of mutation KRAS. The invasive tumors with distinct histological appearances shared the form of noninvasive IPMN as a common precursor, rather than de novo cancer, suggesting the significance of a genetic profiling scheme of tumors associated with IPMN.

Pathologic Evaluation and Reporting of Intraductal Papillary Mucinous Neoplasms of the Pancreas and Other Tumoral Intraepithelial Neoplasms of Pancreatobiliary Tract: Recommendations of Verona Consensus Meeting

BACKGROUND

There are no established guidelines for pathologic diagnosis/reporting of intraductal papillary mucinous neoplasms (IPMNs).

DESIGN

An international multidisciplinary group, brought together by the Verona Pancreas Group in Italy-2013, was tasked to devise recommendations.

RESULTS

(1) Crucial to rule out invasive carcinoma with extensive (if not complete) sampling. (2) Invasive component is to be documented in a full synoptic report including its size, type, grade, and stage. (3) The term "minimally invasive" should be avoided; instead, invasion size with stage and substaging of T1 (1a, b, c; ≤ 0.5, > 0.5-≤ 1, > 1 cm) is to be documented. (4) Largest diameter of the invasion, not the distance from the nearest duct, is to be used. (5) A category of "indeterminate/(suspicious) for invasion" is acceptable for rare cases. (6) The term "malignant" IPMN should be avoided. (7) The highest grade of dysplasia in the non-invasive component is to be documented separately. (8) Lesion size is to be correlated with imaging findings in cysts with rupture. (9) The main duct diameter and, if possible, its involvement are to be documented; however, it is not required to provide main versus branch duct classification in the resected tumor. (10) Subtyping as gastric/intestinal/pancreatobiliary/oncocytic/mixed is of value. (11) Frozen section is to be performed highly selectively, with appreciation of its shortcomings. (12) These principles also apply to other similar tumoral intraepithelial neoplasms (mucinous cystic neoplasms, intra-ampullary, and intra-biliary/cholecystic).

CONCLUSIONS

These recommendations will ensure proper communication of salient tumor characteristics to the management teams, accurate comparison of data between analyses, and development of more effective management algorithms.

Mural nodule of 10 mm or larger as predictor of malignancy for intraductal papillary mucinous neoplasm of the pancreas: Pathological and radiological evaluations

BACKGROUND

We had previously reported that mural nodule (MN) ≥10 mm was optimal predictor of malignancy for intraductal papillary mucinous neoplasm (IPMN). However, little is known about its microscopic findings and imaging detectability.

METHODS

Medical records and resected specimens of consecutive patients with IPMNs harboring MN ≥ 10 mm were reviewed. Imaging detectability was determined on reports basis. Malignant IPMNs (noninvasive + invasive carcinomas) were microscopically classified according to localization of high-grade dysplasia (HGD) within MN.

RESULTS

Thirty-six patients were included. Imaging detectability of MN ≥ 10 mm in CT, MRI, US and EUS were 64%, 68%, 89%, and 97%, respectively. Thirty-three (92%) IPMNs were histologically diagnosed as malignant. Thirty percent of malignant IPMNs were classified into "diffuse HGD within MN", 40% into "focal HGD within MN", and 30% into "HGD outside MN", in which HGD was not located within MN but in low papillary epithelia around MN. Overall sensitivity of pancreatic juice cytology was calculated as 58%, and for "diffuse HGD within MN", "focal HGD within MN", and "HGD outside MN" as 80%, 62%, and 30%, respectively (p = 0.0237). Univariate-analysis showed localization of HGD within MN was associated with true positive cytology (OR = 5.33, p = 0.043).

CONCLUSIONS

Detectability of MN ≥ 10 mm is excellent in US and EUS. Although HGD is observed within MN in 70% of malignant IPMNs, HGD is located only in low papillary epithelia around MN in the remaining 30%, in which sensitivity of pancreatic juice cytology is shown to be inadequate.

Pancreatic main-duct involvement in branch-duct IPMNs: an underestimated risk

OBJECTIVES

This study aimed to analyze a large single-center population of resected intraductal papillary mucinous neoplasms (IPMN) of the pancreas with respect to risk factors of malignant transformation.

BACKGROUND

There is international consensus that main-duct (MD) as well as mixed-type IPMNs should be treated surgically due to a high risk of malignancy. In contrast, there is an ongoing controversy about surgery of branch-duct type IPMN (BD-IPMN).

METHODS

All consecutive patients who underwent surgery for IPMN between January 2004 and December 2012 were included. Clinical characteristics and preoperative imaging were correlated with histopathological features.

RESULTS

A total of 512 patients underwent pancreatic surgery and had a histological proof of IPMN. According to preoperative imaging, 74 patients had MD-IPMN (14%), 205 mixed-type (40%), and 233 suspected BD-IPMN (46%). On histopathology, 162 of 512 patients revealed low-grade, 105 moderate, and 52 high-grade dysplasia. One hundred ninety-three IPMN patients (38%) suffered from invasive carcinoma. Among invasive IPMNs, the majority (58%) were mixed-type lesions according to preoperative imaging. Of 141 Sendai negative BD-IPMNs, a malignancy rate of 18% (high-grade dysplasia and invasive carcinoma) was found. Most interesting, 29% of suspected BD-IPMNs (67/233) revealed histological involvement of the main pancreatic duct not evident in preoperative imaging.

CONCLUSIONS

All subtypes of IPMNs display a relevant risk for malignant transformation. By abdominal imaging, many IPMNs are misclassified as BD-IPMNs but reveal mixed-type lesions in histopathology. Because currently available preoperative diagnostics are not sufficient to reliably diagnose BD-IPMNs, surgical resection for suspected small branch-duct IPMN should be considered in patients fit for surgery.

Pancreatic duct lavage cytology with the cell block method for discriminating benign and malignant branch-duct type intraductal papillary mucinous neoplasms

BACKGROUND

Differentiation between benign and malignant branch-duct type intraductal papillary mucinous neoplasms (IPMNs) remains challenging.

OBJECTIVE

To examine the usefulness of pancreatic duct lavage cytology with cell block method for discriminating benign and malignant branch-duct type IPMNs.

PATIENTS AND METHODS

Between December 2007 and April 2011, patients with branch-duct type IPMNs having mural nodules on EUS were examined by pancreatic duct lavage cytology by using the cell block method. Cell block sections underwent hematoxylin and eosin staining and mucin immunostainings (MUCs 1, 2, 5AC, and 6).

DESIGN

Single-center, prospective study.

SETTING

Academic medical center.

MAIN OUTCOME MEASUREMENTS

The sensitivity and specificity of cytology were assessed. The agreement between cytological and histological results for MUC was also examined.

RESULTS

Cytology with this method was investigated in 44 patients. Cell block diagnosis was cancer positive (class V or IV) in 11 patients and negative (classes I, II, III, and noninformative) in 33. The sensitivity, specificity, and positive and negative predictive values of this method were 92%, 100%, 100%, and 97%, respectively. The cytological and histological results of MUCs 1, 2, 5AC, and 6 agreed in 88% (15/17), 94% (16/17), 88% (15/17), and 100% (17/17), respectively.

LIMITATIONS

Single center and small number of patients.

CONCLUSIONS

Pancreatic duct lavage cytology with the cell block method may be useful to differentiate between benign and malignant IPMNs preoperatively and as well as to determine their mucin type.