Small Bowel Epithelial Precursor Lesions: A Focus on Molecular Alterations

Modified Endoscopic Submucosal Dissection-An Alternative Modality for the Treatment of Sporadic Duodenal Papillary Adenomas

Background and Aim: Endoscopic submucosal dissection (ESD) is commonly employed in the treatment of epithelial gastrointestinal tumors, but few studies have explored ESD for treatment of duodenal papillary adenomas (PAs). In this study, we aim to evaluate the feasibility of a modified ESD method as an alternative modality in the resection of PAs. Methods: We evaluated potential advantages of modified ESD for resection of sporadic duodenal PAs through retrospective analysis of 10 PAs resected via ESD compared to paired lesions undergoing endoscopic papillectomy (EP). Results: All lesions undergoing ESD were resected en bloc with negative margins, compared to 60% of lesions undergoing EP. Within the experimental group, there was one case each of melena and pancreatitis compared to four bleeds and one case of pancreatitis in the control group. No recurrence was detected within the ESD group after a mean follow-up time of 11.2 months compared to three recurrences within a mean follow-up time of 27.7 months. Conclusions: From our preliminary experience, ESD is a promising alternative in the treatment of superficial duodenal PAs; however, further investigation is needed.

Benign Tumors and Tumor-Like Conditions of Ampulla and Small Intestine: The PathologyOutlines.com Review

Small intestine and ampulla can be involved in a heterogeneous group of benign tumors and tumor-like diseases, potentially mimicking malignant neoplasms. In-depth knowledge of them is critical for practicing pathologists since they represent potential pitfalls in routine diagnostic activity. Such conditions include the following: (1) Brunner gland lesions, including Brunner gland hyperplasia and hamartoma; (2) polyps, such as adenoma, hyperplastic, hamartomatous, and inflammatory; (3) mesenchymal proliferations encompassing inflammatory fibroid polyp, inflammatory myofibroblastic tumor, leiomyomas, lipomas, and lipomatosis of the ileocecal valve; (4) fibrosis-associated diseases, such as idiopathic retroperitoneal fibrosis, reactive nodular fibrous pseudotumor, and sclerosing peritonitis; (5) disorders of lymphatic vessels, including lymphangiectasia and lymphangiomas; and (6) other rare conditions/miscellanea, such as enteritis cystica profunda, intussusception, ischemia, and pneumatosis cystoides intestinalis. This review, inspired by the content of the PathologyOutlines website (https://www.pathologyoutlines.com), aims to provide a reference point in this complex scenario, summarizing the essential histopathological features of all these entities for better addressing routine practice and differential diagnoses.

Molecular dynamics of DNA repair and carcinogen interaction: Implications for cancer initiation, progression, and therapeutic strategies

The integrity of the genetic material in human cells is continuously challenged by environmental agents and endogenous stresses. Among these, environmental carcinogens are pivotal in initiating complex DNA lesions that can lead to malignant transformations if not properly repaired. This review synthesizes current knowledge on the molecular dynamics of DNA repair mechanisms and their interplay with various environmental carcinogens, providing a comprehensive overview of how these interactions contribute to cancer initiation and progression. We examine key DNA repair pathways including base excision repair, nucleotide excision repair, and double-strand break repair and their regulatory networks, highlighting how defects in these pathways can exacerbate carcinogen-induced damage. Further, we discuss how understanding these molecular interactions offers novel insights into potential therapeutic strategies. This includes leveraging synthetic lethality concepts and designing targeted therapies that exploit specific DNA repair vulnerabilities in cancer cells. By integrating recent advances in molecular biology, genetics, and oncology, this review aims to illuminate the complex landscape of DNA repair and carcinogen-induced carcinogenesis, setting the stage for future research and therapeutic innovations.

Multimodality imaging features of small bowel cancers complicating Crohn's disease: a pictorial review

Patients with Crohn's disease (CD) are at increased risk of developing small bowel cancer, since chronic inflammation may trigger the histopathological sequence that begins from low-grade dysplasia of the intestinal epithelium and may eventually lead to malignant transformation. Owing to their location in a portion of the gastrointestinal tract which is not easily accessible to conventional endoscopic techniques, the detection of CD-related small bowel cancers is still a clinical challenge. The radiological features of CD-related small bowel adenocarcinoma (SBA) in patients with CD have been described in some previous studies, including its appearance in both CT and MRI examinations. Radiological signs of active or fibrostenotic CD may be intermixed with those suggesting the presence of CD-related SBA. In CT studies, the most relevant findings consistent with malignant transformation are the presence of a stricture with irregular asymmetric thickening of small bowel walls, loss of mural stratification, and moderate enhancement after intravenous administration of iodinated contrast media, in association with enlarged adjacent mesenteric lymph nodes. Many of the CD-related SBA features that can be observed on CT imaging are similar to those detectable by MRI. This latter modality provides the additional value of the functional characterization of small bowel strictures, thereby helping to distinguish between inflammatory, fibrotic, and malignant stenosis in the setting of active CD. Positron Emission Tomography (PET)/CT enables the metabolic assessment of enlarged mesenteric lymph nodes, and PET/MRI fusion imaging can incorporate morphological, functional and metabolic information into a single set of imaging data, thus overcoming the limitations of the separate assessment of each individual modality. Owing to the low incidence and prevalence of this long-term complication of CD, we believe that a detailed multimodality pictorial essay on this topic, also including the PET-CT and fusion imaging documentation of some cases, would be useful to the medical literature.

Pathogenic Insights into DNA Mismatch Repair (MMR) Genes-Proteins and Microsatellite Instability: Focus on Adrenocortical Carcinoma and Beyond

DNA damage repair pathways, including mismatch repair (MMR) genes, are prone to carcinoma development in certain patients. The assessment of the MMR system is widely recognized as part of strategies concerning solid tumors (defective MMR cancers), especially MMR proteins (through immunohistochemistry), and molecular assays for microsatellite instability (MSI). We aim to highlight the status of MMR genes-proteins (including MSI) in the relationship with ACC (adrenocortical carcinoma) according to current knowledge. This is a narrative review. We included PubMed-accessed, full-length English papers published between January 2012 and March 2023. We searched studies on ACC patients for whom MMR status was assessed, respectively subjects harboring MMR germline mutations, namely Lynch syndrome (LS), who were diagnosed with ACC. MMR system assessments in ACCs involve a low level of statistical evidence. Generally, there are two main types of endocrine insights: 1. the role of MMR status as a prognostic marker in different endocrine malignancies (including ACC)-which is the topic of the present work, and 2. establishing the indication of immune checkpoint inhibitors (ICPIs) in selective, mostly highly aggressive, non-responsive to standard care forms upon MMR evaluation (which belongs to the larger chapter of immunotherapy in ACCs). Our one-decade, sample-case study (which, to our knowledge, it is the most comprehensive of its kind) identified 11 original articles (from 1 patient to 634 subjects per study diagnosed with either ACC or LS). We identified four studies published in 2013 and 2020 and two in 2021, three cohorts and two retrospective studies (the publication from 2013 includes a retrospective and a cohort distinct section). Among these four studies, patients already confirmed to have LS (N = 643, respective 135) were found to be associated with ACC (N = 3, respective 2), resulting in a prevalence of 0.0046%, with a respective of 1.4% being confirmed (despite not having a large amount of similar data outside these two studies). Studies on ACC patients (N = 364, respective 36 pediatric individuals, and 94 subjects with ACC) showed that 13.7% had different MMR gene anomalies, with a respective of 8.57% (non-germline mutations), while 3.2% had MMR germline mutations (N = 3/94 cases). Two case series included one family, with a respective four persons with LS, and each article introduced one case with LS-ACC. Another five case reports (between 2018 and 2021) revealed an additional five subjects (one case per paper) diagnosed with LS and ACC (female to male ratio of 4 to 1; aged between 44 and 68). Interesting genetic testing involved children with TP53-positive ACC and further MMR anomalies or an MSH2 gene-positive subject with LS with a concurrent germline RET mutation. The first report of LS-ACC referred for PD-1 blockade was published in 2018. Nevertheless, the use of ICPI in ACCs (as similarly seen in metastatic pheochromocytoma) is still limited. Pan-cancer and multi-omics analysis in adults with ACC, in order to classify the candidates for immunotherapy, had heterogeneous results, and integrating an MMR system in this larger and challenging picture is still an open issue. Whether individuals diagnosed with LS should undergo surveillance for ACC has not yet been proven. An assessment of tumor-related MMR/MSI status in ACC might be helpful. Further algorithms for diagnostics and therapy, also taking into consideration innovative biomarkers as MMR-MSI, are necessary.

Genetic analysis of Japanese patients with small bowel adenocarcinoma using next-generation sequencing

BACKGROUND

Small bowel adenocarcinomas (SBAs) are rare and there is little comprehensive data on SBA genomic alterations for Asian patients. This study aimed to profile genomic alterations of SBA in Japanese patients using targeted next-generation sequencing (NGS).

METHODS

We examined 22 surgical resections from patients with primary SBA. SBA genomic alterations were analyzed by NGS. Mismatch repair (MMR) status was determined by immunohistochemical analysis. Mucin phenotypes were classified as gastric (G), intestinal (I), gastrointestinal (GI), and null (N) types on MUC2, MUC5AC, MUC6, and CD10 immunostaining.

RESULTS

The most common genomic alterations found in SBA tumors were TP53 (n = 16), followed by KRAS (n = 6), APC (n = 5), PIK3CA (n = 4), CTNNB1 (n = 3), KIT (n = 2), BRAF (n = 2), CDKN2A (n = 2), and PTEN (n = 2). Deficient MMR tumors were observed in 6 out of 22 patients. Tumor mucin phenotypes included 2 in G-type, 12 in I-type, 3 in GI-type, and 5 in N-type. APC and CTNNB1 mutations were not found in G-type and GI-type tumors. KRAS mutations were found in all tumor types except for G-type tumors. TP53 mutations were found in all tumor types. Although no single gene mutation was associated with overall survival (OS), we found that KRAS mutations were associated with significant worse OS in patients with proficient MMR tumors.

CONCLUSIONS

SBA genomic alterations in Japanese patients do not differ significantly from those reports in Western countries. Tumor localization, mucin phenotype, and MMR status all appear to impact SBA gene mutations.

Mucosal defense: gastroduodenal injury and repair mechanisms

PURPOSE OF REVIEW

The mucosal barrier serves as a primary interface between the environment and host. In daily life, superficial injury to the gastric or duodenal mucosa occurs regularly but heals rapidly by a process called 'restitution'. Persistent injury to the gastroduodenal mucosa also occurs but initiates a regenerative lesion with specific wound healing mechanisms that attempt to repair barrier function. If not healed, these lesions can be the site of neoplasia development in a chronic inflammatory setting. This review summarizes the past year of advances in understanding mucosal repair in the gastroduodenal mucosa, which occurs as a defense mechanism against injury.

RECENT FINDINGS

Organoids are an emerging new tool that allows for the correlation of in vivo and in vitro models; organoids represent an important reductionist model to probe specific aspects of injury and repair mechanisms that are limited to epithelial cells. Additionally, proof-of-concept studies show that machine learning algorithms may ultimately assist with identifying novel, targetable pathways to pursue in therapeutic interventions. Gut-on-chip technology and single cell RNA-sequencing contributed to new understanding of gastroduodenal regenerative lesions after injury by identifying networks and interactions that are involved in the repair process.

SUMMARY

Recent updates provide new possibilities for identifying novel molecular targets for the treatment of acute and superficial mucosal injury, mucosal regeneration, and regenerative lesions in the gastrointestinal tract.