Unveiling the intriguing relationship: oncogenic KRAS, morphological shifts, and mutational complexity in pancreatic mucinous cystic neoplasms

Abstract

Pancreatic ductal adenocarcinoma (PDAC) often arises from preexisting cystic lesions such as intraductal papillary mucinous neoplasms (IPMN) and mucinous cystic neoplasms (MCN). This study investigated the molecular heterogeneity and mutational landscape of MCN in relation to PDAC, highlighting the significance of KRAS mutations in tumor progression. Utilizing targeted next-generation sequencing on low-grade MCN and invasive PDAC samples, we identified a substantial overlap in mutational profiles, particularly mutations in KRAS, TP53, and FBXW7. Specifically, 69.2% of MCN exhibited somatic mutations, with KRAS mutations being a predominant oncogenic driver. The characterization of mutant versus wildtype KRAS variant allele frequencies (VAF) indicated higher mutation levels in PDAC compared to MCN, suggesting an evolutionary trajectory toward malignancy. Further histological analysis of 12 additional MCN cases revealed significant intratumor heterogeneity, with variant KRAS mutation distributions correlating with distinct cellular morphologies and dysplastic features. Additionally, we explored the potential of liquid biopsies, demonstrating a concordance rate of 71.4% for KRAS mutation detection in circulating tumor DNA (ctDNA) relative to tissue biopsies across cohorts. Our findings underscore the relevance of evaluating KRAS mutations-herein referred to as VAF per microdissected region-as they relate to histopathological markers of dysplasia, contributing to improved stratification of pancreatic lesions and facilitating personalized treatment strategies. In conclusion, this comprehensive analysis of MCN highlights the importance of KRAS as a crucial biomarker for both malignant progression and therapeutic decision-making in pancreatic pathology. Ultimately, our study suggests that characterizing the mutational landscape and histological features of MCN can enhance early detection and intervention strategies for at-risk patients. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Keywords: KRAS mutations; circulating tumor DNA (ctDNA); intratumor heterogeneity; mucinous cystic neoplasms (MCN); mutational landscape; pancreatic ductal adenocarcinoma (PDAC); tumor progression; variant allele frequency (VAF).

Figure 1

Comprehensive analysis of KRAS mutations and histological features in MCN. (A) Schematic representation of the workflow used to investigate the mutational status of PDAC and MCN samples and introduction of the three independent cohorts (Cohort 1, MCN‐1, and PDAC‐1, Heidelberg: tissue and partially plasma; Cohort 2, MCN‐2, Ulm: only tissue; Cohort 3, MCN‐3, Heidelberg: only plasma). (B) Left: Scheme of the chosen panel sequencing approach to analyze Cohort 1 (tissue of PDAC and MCN). Right: Histologic sections of PDAC, MCN, and MCN adjacent tissues from Cohort 1 stained by hematoxylin–eosin (HE). The circular diagrams inlaying each image display the mutational burden across the three types of analyzed tissue. (C) Heatmap showing somatic gene mutations allelic frequencies in the MCN‐1 (left panel) and PDAC‐1 (right panel) cases from Cohort 1 (D) Somatic mutations frequency in tissue from the MCN‐1 and PDAC‐1 Cohort 1. (E) Venn diagram showing the overlap of mutated genes between MCN‐1 and PDAC‐1 cases from Cohort 1. (F) Mean of variant allelic frequencies of somatic mutations in tissue from the MCN‐1 and PDAC‐1 Cohort 1. (G) Histologic sections of unmutated and mutated KRAS MCN from Cohort 2. (H) Circular diagram indicating the percentage of MCN cases in Cohort 2 carrying at least one microdissected area per MCN a KRAS G12/G13 mutation as measured using ddPCR. (I) Diagram showing total amount of microdissected areas and corresponding number of KRAS mutant areas per MCN case in Cohort 2. (J) KRAS mutant allelic frequency in cuboidal, columnar, papillary, and nuclei pseudostratified regions of MCN from Cohort 2. (K) Heatmap depicting the KRAS mutational status in the tissue and in a corresponding plasma ctDNA sample, if available, from the MCN cases in Cohort 1 (upper panel). KRAS mutational status assessed in Cohort 3 for which only plasma samples but no tissues were available (lower panel). Panel A was created with BioRender.com.