Genomic Profiling of Rare Undifferentiated Sarcomatoid Subtypes of Pancreatic Carcinomas: In Search of Therapeutic Targets.

PURPOSE: The highly aggressive undifferentiated sarcomatoid carcinoma (USC) subtype of pancreatic ductal adenocarcinoma (PDAC) remains poorly characterized because of its rarity. Previous case reports suggest that immune checkpoint inhibitors could be a promising treatment strategy, but the prevalence of established predictive biomarkers of response is largely unknown. The objective of this study was to leverage comprehensive genomic profiling of USC PDAC tumors to determine the prevalence of biomarkers associated with potential response to targeted therapies. METHODS: USC tumors (n = 20) underwent central pathology review by a board-certified gastrointestinal pathologist to confirm the diagnosis. These samples were compared with non-USC PDAC tumors (N = 5,562). Retrospective analysis of DNA and RNA next-generation sequencing data was performed. RESULTS: USC PDACs were more frequently PD-L1+ by immunohistochemistry than non-USC PDAC (63% v 16%, respectively, P < .001). Furthermore, USC PDAC had an increase in neutrophils (8.99% v 5.55%, P = .005) and dendritic cells (1.08% v 0.00%, q = 0.022) and an increased expression of PDCD1LG2 (4.6% v 1.3%, q = 0.001), PDCD1 (2.0% v 0.8%, q = 0.060), and HAVCR2 (45.9% v 21.7%, q = 0.107) than non-USC PDAC. Similar to non-USC PDAC, KRAS was the most commonly mutated gene (86% v 90%, respectively, P = 1). CONCLUSION: To our knowledge, this work represents the largest molecular analysis of USC tumors to date and showed an increased expression of immune checkpoint genes in USC tumors. These findings provide evidence for further investigation into immune checkpoint inhibitors in USC tumors.

Efficacy and Toxicity Analysis of mFOLFIRINOX in High-Grade Gastroenteropancreatic Neuroendocrine Neoplasms.

BACKGROUND: High-grade neuroendocrine neoplasms (NENs) comprise both well-differentiated grade 3 neuroendocrine tumors (G3 NETs) and poorly differentiated neuroendocrine carcinomas (NECs). Mixed neuroendocrine-non-neuroendocrine neoplasms (MiNENs) nearly always include poorly differentiated NEC as the neuroendocrine component. The efficacy and safety of frontline mFOLFIRINOX chemotherapy has never been investigated in patients with high-grade NENs. PATIENTS AND METHODS: We conducted a multi-institutional retrospective analysis of patients with advanced high-grade NEN of the gastroenteropancreatic tract or of unknown origin seen between February 2016 and April 2023 who received treatment with frontline mFOLFIRINOX. RESULTS: A total of 35 patients were included (G3 NETs: n=2; NECs: n=25; MiNENs: n=8; stage III: n=5; stage IV: n=30). The objective response rate was 77% (complete response: 3%; partial response: 74%). Median progression-free survival was 12 months (95% CI, 9.2-16.2 months) and median overall survival was 20.6 months (95% CI, 17.2-30.6 months). No significant differences in efficacy were seen according to primary site, histopathology, and Ki-67 proliferative index. All 5 patients with stage III disease who received mFOLFIRINOX obtained an objective response and underwent radical surgery or definitive radiotherapy with curative intent, with a recurrence rate of 40%. Grade 3 or 4 adverse events were observed in 43% of patients (mainly neutropenia and diarrhea). Females were at significantly increased risk of developing severe toxicities. CONCLUSIONS: mFOLFIRINOX shows antitumor activity against high-grade NENs. Well-designed, prospective clinical trials are needed to assess the efficacy of mFOLFIRINOX in both the neoadjuvant and metastatic settings.

Genomic determinants of biological aggressiveness and poor prognosis of pancreatic cancers: KRAS and beyond.

INTRODUCTION: A marked histomolecular heterogeneity characterizes pancreatic cancer. Thus, different tumor histologies with divergent genomic profiles exist within the same category. AREAS COVERED: Using data from PubMed, SCOPUS, and Embase (last search date: 04/04/2024), this expert-based, narrative review presents and discusses the essential molecular determinants of biological aggressiveness and poor prognosis in pancreatic cancer. First, KRAS mutation still represents one of the most critical difficulties in treating pancreatic cancers. In this district, it is mutated in > 90% of malignant tumors. Notably, actionable alterations for molecular-based therapies are typically lacking in KRAS-mutated pancreatic cancer. Furthermore, transcriptome-based studies clarified that the squamous phenotype is characterized by poorer prognosis and response to standard chemotherapy. We also discuss molecular biomarkers related to dismal prognosis in specific subsets of pancreatic cancer, such as SMAD4 in signet-ring cell carcinoma and TP53 in invasive cancers derived from intraductal tubulopapillary neoplasms. EXPERT OPINION: The identification of the subgroups of pancreatic cancer with particularly unfavorable prognoses is a critical step for addressing specific research efforts. In addition to implementing and strengthening current precision oncology strategies, the decisive step for improving the survival of patients affected by pancreatic cancer must pass through targeting the KRAS gene.

Reappraising the Role of Intraoperative Neck Margin Revision in Post-Neoadjuvant Pancreatoduodenectomy for Pancreatic Ductal Adenocarcinoma: A Multi-Institutional Analysis.

OBJECTIVE: To investigate whether revision of pancreatic neck margin based on intraoperative frozen section analysis has oncologic value in post-neoadjuvant pancreatoduodenectomy (PD) for pancreatic ductal adenocarcinoma (PDAC). SUMMARY BACKGROUND DATA: The role of intraoperative neck margin revision has been controversial, with little information specific to post-neoadjuvant PD. METHODS: Patients who underwent post-neoadjuvant PD (2013-2019) for conventional PDAC with frozen section analysis of neck margin at three academic institutions were included. Overall survival (OS) and recurrence-free survival (RFS) were compared across three groups: complete resection achieved en-bloc (CR-EB), complete resection achieved non-en-bloc (CR-NEB), and incomplete resection (IR). RESULTS: Among the 671 patients included, 524 (78.1%) underwent CR-EB, 119 (17.7%) CR-NEB and 28 (4.2%) IR. Patients undergoing CR-NEB and IR exhibited larger tumors and lower rates of RECIST response, requiring vascular resections more often. Likewise, CR-NEB and IR were associated with a worse pathological profile than CR-EB. The incidence of postoperative complications and access to adjuvant treatment were comparable among groups. A CR-EB was associated with the longest OS duration (34.3 mo). In patients with positive neck margin, obtaining a CR-NEB via re-excision was associated with a comparable OS relative to patients with an IR (26.9 vs. 27.1 mo, P=0.901). Similar results were observed for RFS. At multivariable analysis, neck margin status was not independently associated with survival and recurrence. CONCLUSION: Conversion of an initially positive pancreatic neck margin by additional resection is not associated with oncologic benefits in post-neoadjuvant PD and cannot be routinely recommended.

Gastric Carcinoma in Autoimmune Gastritis: A Histopathologic and Molecular Study.

Patients with autoimmune gastritis (AIG) have a 13-fold risk of developing type-1 neuroendocrine tumors, whereas the risk for gastric adenocarcinoma is still uncertain. Here we describe the clinicopathologic and molecular features of a series of gastric carcinomas (GC) arising in the context of AIG. A total of 26 AIG-associated GC specimens were collected from 4 Italian Institutions. Immunohistochemistry for MUC1, MUC2, MUC5AC, MUC6, CDX2, HER2, PD-L1, CLDN18, mismatch repair (MMR) proteins, and p53 and EBV-encoded RNA (EBER) in situ hybridization were performed. Histologic and immunohistochemical features were jointly reviewed by 5 expert gastrointestinal pathologists. Next-generation sequencing analysis (TrueSight Oncology 500, Illumina) of 523 cancer-related genes was performed on 19 cases. Most tumors were diagnosed as pT1 (52%) and they were located in the corpus/fundus (58%) and associated with operative link for gastritis assessment stage II gastritis (80.8%), absence of parietal cells, complete intestinal metaplasia, and enterochromaffin-like-cell micronodular hyperplasia. Only 4 (15.4%) GCs were diagnosed during follow-up for AIG. The following histotypes were identified: 20 (77%) adenocarcinomas; 3 (11%) mixed neuroendocrine-non-neuroendocrine neoplasms, and 2 (8%) high-grade solid adenocarcinomas with focal neuroendocrine component, 1 (4%) adenocarcinoma with an amphicrine component. Overall, 7 cases (27%) showed MMR deficiency, 3 (12%) were positive (score 3+) for HER2, 6 (23%) were CLDN18 positive, and 11 (42%) had PD-L1 combined positive score ≥ 10. EBER was negative in all cases. Molecular analysis revealed 5/19 (26%) microsatellite instability (MSI) cases and 7 (37%) tumor mutational burden (TMB) high. The most frequently altered genes were TP53 (8/19, 42%), RNF43 (7/19, 37%), ERBB2 (7/19, 37% [2 amplified and 5 mutated cases]), ARID1A (6/19, 32%), and PIK3CA (4/19, 21%). In summary, AIG-associated GCs are often diagnosed at low stage in patients with longstanding misrecognized severe AIG; they often display a neuroendocrine component or differentiation, have relatively higher rates of MMR deficiency, and TMB high.

Forensic value of soft tissue detachments from the hyoid bone in death due to strangulation asphyxia.

BACKGROUND: There are no unequivocal histopathological findings for the diagnosis of fatal asphyxia due to neck compression. From the observation of a series of asphyxiation cases, we noted, during microscopic analysis, a high frequency of "detachment" of soft tissues from the hyoid bone. This specifically refers to the presence of an optical space between the surface of the hyoid bone and soft tissues. OBJECTIVES: We aimed to evaluate the detachment of soft tissues from the hyoid bone as specific histological evidence of death due to strangulation asphyxia. MATERIAL AND METHODS: Ten blocks were taken from deaths due to external mechanical compression of the neck (strangulation asphyxia, group A), 22 blocks were taken from deaths for other causes without trauma to the neck (group B), and 38 blocks were obtained from living subjects that have undergone laryngectomies (group C). The presence/absence of detachments were compared between the 3 groups (A, B and C) using Fisher's exact test. RESULTS: The detachment of soft tissues from the hyoid bone was observed in 5 cases (50%) in group A, 6 cases (27.2%) in group B, and 17 cases (44.3%) in group C. The sensitivity and specificity of the presence of the detachment in group A were 0.5 (95% confidence interval (95% CI): 0.38-0.62) and 0.57 (95% CI: 0.45-0.69), respectively. The comparison between the 3 groups and the presence/absence of soft tissue detachment showed no statistically significant differences between the groups (p = 0.329), clarifying that soft tissue detachment is a nonspecific variable for all 3 situations. CONCLUSIONS: Detachment of soft tissues has poor value as a single element to favor the diagnosis of asphyxia due to violent compression of the neck and should be interpreted as an artifactual finding, unrelated to the neck injury or injury vitality.

Fusion genes in pancreatic tumors.

Gene fusions and rearrangements play a crucial role in tumor biology. They are rare events typically detected in KRAS wild-type (WT) pancreatic tumors. Their identification can inform clinical management by enabling precision oncology, as fusions involving BRAF, FGFR2, RET, NTRK, NRG1, and ALK represent actionable targets in KRAS-WT cancers, and serve diagnostic purposes since fusions involving PRKACA/B represent the diagnostic hallmark of intraductal oncocytic papillary neoplasms (IOPNs). Although they are rare, the therapeutic and diagnostic importance of these genomic events should not be underestimated, highlighting the need for quality-ensured molecular diagnostics in the management of cancer. Herein we review the existing literature on the role of fusion genes in pancreatic tumors and their clinical potential as effective biomarkers and therapeutic targets.

DNA Methylation Profiling Enables Accurate Classification of Nonductal Primary Pancreatic Neoplasms.

BACKGROUND & AIMS: Cytologic and histopathologic diagnosis of non-ductal pancreatic neoplasms can be challenging in daily clinical practice, whereas it is crucial for therapy and prognosis. The cancer methylome is successfully used as a diagnostic tool in other cancer entities. Here, we investigate if methylation profiling can improve the diagnostic work-up of pancreatic neoplasms. METHODS: DNA methylation data were obtained for 301 primary tumors spanning 6 primary pancreatic neoplasms and 20 normal pancreas controls. Neural Network, Random Forest, and extreme gradient boosting machine learning models were trained to distinguish between tumor types. Methylation data of 29 nonpancreatic neoplasms (n = 3708) were used to develop an algorithm capable of detecting neoplasms of non-pancreatic origin. RESULTS: After benchmarking 3 state-of-the-art machine learning models, the random forest model emerged as the best classifier with 96.9% accuracy. All classifications received a probability score reflecting the confidence of the prediction. Increasing the score threshold improved the random forest classifier performance up to 100% with 87% of samples with scores surpassing the cutoff. Using a logistic regression model, detection of nonpancreatic neoplasms achieved an area under the curve of >0.99. Analysis of biopsy specimens showed concordant classification with their paired resection sample. CONCLUSIONS: Pancreatic neoplasms can be classified with high accuracy based on DNA methylation signatures. Additionally, non-pancreatic neoplasms are identified with near perfect precision. In summary, methylation profiling can serve as a valuable adjunct in the diagnosis of pancreatic neoplasms with minimal risk for misdiagnosis, even in the pre-operative setting.

Diagnostic Pearls and Pitfalls in the Evaluation of Biopsies of the Pancreas.

CONTEXT.­: The examination of small pancreatic biopsies is a difficult task for pathologists. This is due to the scant and fragmented material often obtained from diagnostic procedures as well as the significant overlap between different neoplastic and nonneoplastic entities. In the upcoming neoadjuvant era, biopsies could become even more important, representing the only possibility to look at the real histomorphology of tumors before chemotherapy-induced modifications. OBJECTIVES.­: To summarize and discuss the state-of-the-art diagnostic workflow for small pancreatic biopsies, including the most important morphologic and immunohistochemical features and molecular alterations. The main diagnostic pearls and pitfalls of this challenging scenario are also discussed. The most important topics of this review are represented by: (1) pancreatic ductal adenocarcinoma, along with its main differential diagnoses, including autoimmune pancreatitis; (2) solid hypercellular neoplasms, including neuroendocrine neoplasms, acinar cell carcinoma, pancreatoblastoma, and solid pseudopapillary neoplasms; and (3) cystic lesions. Real-world considerations will be also presented and discussed. DATA SOURCES.­: Sources included a literature review of published studies and the author's own work. CONCLUSIONS.­: The correct diagnosis of pancreatic lesions is a crucial step in the therapeutic journey of patients. It should be based on robust, standardized, and reliable hallmarks. As presented and discussed here, the integration of morphology with immunohistochemistry, and in selected cases, with molecular analysis, represents a decisive step in this complex scenario.

The Italian Rare Biliary tract Cancer initiative (IRaBiCa): A multicentric observational study of Gruppo Oncologico dell'Italia Meridionale (GOIM) in collaboration with Gruppo Italiano Colangiocarcinoma (GICO).

INTRODUCTION: About 90% of cholangiocarcinomas are adenocarcinomas with glandular or tubular structures lined by epithelial cells, with no bile production and with a variable degree of differentiation, arising in the background of desmoplastic stroma. The remaining 10% is represented by rarer histological variants of which there is little knowledge regarding the biological behavior, molecular characterization, and sensitivity to the various possible therapies, including molecular-based treatments. Such rare tumors are described only in case reports or small retrospective series because of their exclusion from clinical trials. This national initiative, here presented, aims to address the following knowledge gap: a) how much does histological diversity translate into clinical manifestation variety? b) are those chemotherapy regimens, recommended for conventional biliary tract cancers, potentially active in rare variants?Therefore, epidemiological, pathological, and clinical characterization of series of rare biliary histotypes/variants, for which therapeutic and follow-up data are available, will be collected. METHODS: An Italian task force on rare tumors of the biliary tract (IRaBiCa) has been created, whose initiative is a multicenter retrospective study involving 34 Italian cancer centers.Clinical data from approximately 100 patients will be collected and analyzed. Continuous variables will be presented as median ± standard deviation, while categorical variables will be expressed in terms of frequency. Kaplan-Maier analyses will be used to compare disease free, progression free and overall survival, according to the different histotypes. CONCLUSIONS: We expect to gather novel data on rare histotypes of biliary tract cancer that will be useful to support their molecular and immunological characterization.

Claudin-18.2 testing and its impact in the therapeutic management of patients with gastric and gastroesophageal adenocarcinomas: A literature review with expert opinion.

Claudin-18.2 (CLDN18.2) is a member of the tight junction protein family and is a highly selective biomarker with frequent abnormal expression during the occurrence and development of various primary malignant tumors, including gastric cancer (GC) and esophago-gastric junction adenocarcinomas (EGJA). For these reasons, CLDN18.2 has been investigated as a therapeutic target for GC/EGJA malignancies. Recently, zolbetuximab has been proposed as a new standard of care for patients with CLDN18.2-positive, HER2-negative, locally advanced and metastatic GC/EGJA. The use of CLDN18 IHC assays to select patients who might benefit from anti-CLDN18.2 therapy is currently entering clinical practice. In this setting, pathologists play a central role in therapeutic decision-making. Accurate biomarker assessment is essential to ensure the best therapeutic option for patients. In the present review, we provide a comprehensive overview of available evidence on CLDN18.2 testing and its impact on the therapeutic management of patients with GC/EGJA, as well as some practical suggestions for CLDN18.2 staining interpretation and potential pitfalls in the real-world setting.

Impact of extra-ampullary duodenal adenocarcinoma subtypes on surgical and oncological outcomes following pancreaticoduodenectomy.

BACKGROUND: There is little information about the relevance of extra-ampullary duodenal adenocarcinoma (EDA) subtypes. The aim of this study was to evaluate the impact of EDA subtypes on surgical and oncological outcomes following pancreatoduodenectomy (PD). METHODS: Consecutive patients undergoing PD for EDA from 2000 to 2019 were analyzed. Results were stratified by pathologic subtype (intestinal versus non-intestinal). Uni-and multivariable analyses were performed using standard statistical methods. RESULTS: The study population consisted of 70 patients, of whom 49 (70%) had an intestinal phenotype. EDA with intestinal phenotype was more frequently proximal to the Ampulla of Vater, while non-intestinal EDA was more frequently found distally (76% vs. 33%, p = 0.002). Patients with intestinal EDA were less likely to experience severe morbidity, with decreased reoperation and unplanned Intensive Care Unit admission rates relative to non-intestinal subtypes (2% vs. 29% p = 0.002, and 2% vs. 19%, p = 0.007, respectively). The median follow-up post-pancreatectomy was 73 months. Intestinal EDA was associated with improved overall and disease-free survival, with 3-year and 5-year survival rates of 71% vs. 29% and 53% vs. 24%, respectively. (p = 0.019 and p = 0.025). CONCLUSION: Intestinal-type EDA, which more often arises from supra-ampullary duodenum, was associated with better postoperative outcomes and improved survival.

Perioperative NALIRIFOX in patients with resectable pancreatic ductal adenocarcinoma: The open-label, multicenter, phase II nITRO trial.

BACKGROUND: Upfront surgery followed by postoperative treatment is a commonly adopted treatment for resectable pancreatic ductal adenocarcinoma (rPDAC). However, the risk of positive surgical margins, the poor recovery that often impairs postoperative treatments, and the risk of recurrence might limit the outcome of this strategy. This study evaluated the safety and the activity of liposomal irinotecan 50 mg/m2 + 5-fluorouracil 2400 mg/m2 + leucovorin 400 mg/m2 + oxaliplatin 60 mg/m2 (NALIRIFOX) in the perioperative treatment of patients with rPDAC. METHODS: Eligible patients had a rPDAC with < 180° interface with major veins' wall. Patients received 3 cycles before and 3 cycles after resection with NALIRIFOX, days 1 and 15 of a 28-day cycle. The primary endpoint was the proportion of patients undergoing an R0 resection. RESULTS: 107 patients began preoperative treatment. Nine patients discontinued the treatment because of related or unrelated adverse events. Disease-control rate was 92.9%. 87 patients underwent surgical exploration, 11 had intraoperative evidence of metastatic disease, and 1 died for surgical complications. R0 resection rate was 65.3%. 49 patients completed the three postoperative cycles. The most common grade ≥ 3 adverse events were diarrhea and neutropenia. Median overall survival (OS) of ITT patients was 32.3 months (95% CI 27.8-44.3). Median disease-free and OS from surgery of resected patients were 19.3 (95% CI 12.6-34.1) and 40.3 months (95% CI 29-NA), respectively. CONCLUSION: Perioperative NALIRIFOX was manageable and active, and deserves further investigation in randomized trials comparing it with standard upfront surgery followed by adjuvant therapy.

Prevalence and type of MMR expression heterogeneity in colorectal adenocarcinoma: therapeutic implications and reporting.

Mismatch repair (MMR) immunohistochemical (IHC) evaluation has entered pathology routine practice as the first-line screening method to identify patients with MMR deficient (MMRd)/microsatellite instability (MSI) colorectal cancer (CRC), and its misdiagnosis may significantly impact the personalization of CRC patient care. To determine the prevalence of MMR protein intratumor heterogeneity in real-world practice, we collected a series of 8282 CRCs tested for MMR proteins in the setting of Lynch syndrome universal screening. Four heterogenous cases were also investigated for tumor infiltrating lymphocytes count, MSI status, and consensus molecular subtypes by Nanostring nCounter® Platform. Overall, 1056 (12.8%) CRCs showed a MMR altered status, with 46 cases showing a heterogeneous MMR profile (0.56% of the total, and 4.36% of all MMRd cases). To conclude, the authors make some critical remarks regarding the approach to MMR heterogeneity in clinical practice and routine diagnostics.

Systematic review of challenging issues in pathology of intraductal papillary mucinous neoplasms.

BACKGROUND: Intraductal papillary mucinous neoplasms (IPMNs) are a cystic precursor to pancreatic cancer. IPMNs deemed clinically to be at high-risk for malignant progression are frequently treated with surgical resection, and pathological examination of the pancreatectomy specimen is a key component of the clinical care of IPMN patients. METHODS: Systematic literature reviews were conducted around eight topics of clinical relevance in the examination of pathological specimens in patients undergoing resection of IPMN. RESULTS: This review provides updated perspectives on morphological subtyping of IPMNs, classification of intraductal oncocytic papillary neoplasms, nomenclature for high-grade dysplasia, assessment of T stage, distinction of carcinoma associated or concomitant with IPMN, role of molecular assessment of IPMN tissue, role of intraoperative assessment by frozen section, and preoperative evaluation of cyst fluid cytology. CONCLUSIONS: This analysis provides the foundation for data-driven approaches to several challenging issues in the pathology of IPMNs.

Recurrent gastric amphicrine tumor with neuroendocrine and pancreatic acinar cell differentiation and somatic MEN1 inactivation arisen during immunotherapy.

Amphicrine neoplasms (ANs) are poorly understood epithelial malignancies composed of cells with co-existing exocrine-neuroendocrine features. Here, we report a recurrent mucin-producing gastric amphicrine tumor co-expressing neuroendocrine (chromogranin-A, synaptophysin, and CD56) and pancreatic acinar cell (BCL10 and trypsin) markers, arisen in a 64-year-old woman during adjuvant immunotherapy for melanoma. Ki-67 was < 2%. The gastric background context was atrophic gastritis. Next-generation sequencing showed MEN1 mutation (p.P71fs*42) coupled with loss of heterozygosity. The key lessons were as follows: (1) gastric ANs can show the co-existence of exocrine mucin-producing elements with neuroendocrine and pancreatic acinar differentiation; (2) they may represent a new entity arising in the context of atrophic gastritis and during immunotherapy; (3) they should be considered in the diagnostic workup of gastric neuroendocrine tumors; and (4) their molecular profile can show striking similarities with well-differentiated neuroendocrine tumors. These findings may be of help to improve the knowledge and the biological taxonomy of ANs.

Comprehensive characterisation of acinar cystic transformation of the pancreas: a systematic review.

AIMS: Acinar cystic transformation (ACT) of the pancreas is a rare pancreatic cystic lesion. Owing to its rarity, comprehensive histomolecular characterisation of this entity is still lacking. We aim to perform a systematic review on this controversial entity. METHODS: We searched PubMed, SCOPUS and Embase through May 2023 to identify all studies on ACTs. Clinicopathological, immunohistochemical (IHC) and molecular data have been extracted and analysed. RESULTS: Overall, there were 121 cases of ACTs in the literature. ACT had a female predominance (65.3% of patients), and a mean size of 4.8 cm. ACT was more often unifocal (71.9%) and multiloculate (61.2%). Histologically, the cysts were lined by an acinar epithelium, sometimes harbouring ductal-like areas (18.2%). In five cases (4.1%), an intralesional pancreatic intraepithelial neoplasia (PanIN) was reported. Preoperative diagnosis is challenging. After surgical resection, all patients were alive and disease free during follow-up except one patient who developed a second ACT after resection. By IHC, all lesions were positive for acinar markers; cytokeratin 7 and 8/18/19 were usually positive, and Ki-67 was invariably ≤3%. At the molecular level, three cases demonstrated genetic alterations: one showed multiple chromosomal gains, and other two harboured somatic mutations of KRAS and SMO genes (one mutation per case). CONCLUSIONS: Globally considered, our findings demonstrated that ACT is a benign entity, without the need of surgical resection with the exception of symptomatic lesions. The rare occurrence of intracystic PanINs and driver mutations suggest considering follow-up if a preoperative diagnosis of ACT can be made.