# Introduction runner glands (BG), first described by the swiss anatomist Johann Conrad Brunner in 1688, 1 arelocated predominantly in the submucosa of the proximal duodenum and are composed of cells with columnar to cuboidal cytoplasm and basal nuclei, arranged in lobules separated by delicate fibrous septa. They secrete alkaline mucus (composed of mucin glycoproteins, bicarbonate and various additional factors including epidermal growth factor, trefoil peptides, bactericidal factors, proteinase inhibitors, and surface-active lipids) that protect the epithelium from digestive enzymes. 2 The exact classification of Brunner glandlesions (BGL) is evolving and hyperplasia (BGH), adenoma (BGA), hamartoma and brunneroma, have been used as descriptors. In general, lesions smaller than 0.5 cm are considered hyperplasia and not true neoplasias. 3 Historically, BGL/BGH were first classified by Feyrter into three types: type 1 (diffuse nodular hyperplasia with sessile projections extending beyond the duodenal bulb), type 2 (nodular or sessile hyperplasia confined to the duodenal bulb), and type 3 (pedunculated or sessile adenoma forming a mass). 4 However, a clear pathologic distinction based on clinical pathologic correlation has not been developed and the malignant potential of these benign lesions remains uncertain. 5 BGL represent less than 1% of primary tumors in the small intestine, and approximately 10% of duodenal neoplasms. Rare reports have documented possible progression to carcinoma, 6 and presenting symptoms vary widely according to the size of the lesions. They tend to be asymptomatic until growing Author: e-mail: victor.nava@va.gov beyond 1.5 cm, while tumors larger than 2 cm may manifest with upper gastrointestinal bleeding and obstruction. 3 The literature on genetic alterations in BGL is sparse and devoid of KRAS hits. We report the case of a 64-year-old male with a 1.5 cm polyp in the duodenum corresponding to a BGH type 3/BGA with a point mutation (G12D) in KRAS. # II. # Case Report A 64-year-old male with history of heart failure with reduced ejection fraction, chronic renal failure stage 5, coronary artery disease, diabetes mellitus, hypertension, stroke, benign prostatic hyperplasia and tobacco use disorder, presented to the hospital for a nephrology follow up visit. Detection of combined iron deficiency and chronic disease anemia (decreased hemoglobin 6.6 g/dl, hematocrit 20.6 % and iron 34 ug/dL; with normal MCV 91.7 fL, and ferritin 69 ng/ml) prompted upper endoscopy and colonoscopy. The upper endoscopy showed a 1.5 cm, pink-tan polyp in the duodenum, which was resected. The histopathological examination revealed BGA/BGH type 3 without dysplasia or malignancy (Figure 1 & 2). Immunohistochemistry revealed intact expression of DNA mismatch repair proteins (MLH1, MSH2, MSH6 and PMS2) supporting lack of microsatellite instability. Due to the rarity of the lesion next generation sequencing (Oncomine Focus, ThermoFisher) was performed on extracted DNA revealing a KRAS G12D genetic alteration. In addition, the colonoscopy revealed three tubular adenomas (one 0.4 cm pedunculated polyp in the ascending colon and two sessile polyps ranging from 0.3 to 0.5 cm in the transverse colon). Of note, the patient died three months later due to respiratory failure from SARS-CoV-2 infection. # III. # Discussion BGL present most commonly as an incidental endoscopic finding in asymptomatic patients during their fifth or sixth decade of life without a predilection towards gender or race. 7 Although BG proliferations are traditionally considered benign they can be premalignant 8 and develop dysplasia and even invasive carcinoma in ~2% and 0.3% of cases, respectively. 9 However, the exact molecular pathogenesis is unknown. Brosens et al. reported a BG hamartoma in one patient with juvenile polyposis syndrome harboring a germline mutation in SMAD4/DPC4, a highly conserved transcription factor activated by TGF-?. 10 Loss of the tumor suppressor LRIG1 (a transmembrane protein that interacts with EGFR family proteins) has been associated with increased proliferation of Brunner glands in mice and intestinal adenomatous polyps in humans. 11 In addition, Levi et al. described BGH smaller than 1 cm in 20% of 10 patients with Cowden syndrome (CS), 12 suggesting a pathogenic role for PTEN mutations, which are present in ~85% of patients affected by this syndrome. Mutations in the Kirsten rat sarcoma viral oncogene homologue (KRAS) have not been previously reported in BGL to the best of our knowledge. This wellknown proto-oncogene encodes a protein that acts as a molecular switch transducing extracellular signals from membrane receptors (like EGRF) to the cytosolic MAPK and PI3K/mTOR pathways, ultimately leading to activation of nuclear transcription controlling cell proliferation, differentiation, and survival. 13 KRAS is mutated in approximately 25% of human tumors, representing one of the most commonly altered genes associated with cancer. 14 Missense mutations in KRAS stabilize an active GTP-bound form of the protein promoting oncogenesis. The G12D point mutation we identified in a BGA is a well-recognized and powerful cancer driver mutation with impaired GTPase catalytic activity. 15 It is also the most prevalent alteration in human cancer, which is present in 4.2% of cases in the American Association of Cancer Research public database. 16 Interestingly, KRAS G12D is embryonic lethal in mouse models, but is sufficient to initiate transformation of fibroblasts in cell culture and to induce preneoplastic epithelial hyperplasias in the lung and gastrointestinal tract. 17 Because there is crosstalk between the MAPK, PTEN/PI3K and TGF-?/BMP pathways, 18 it is possible that other altered genes (SMAD4, LRIG1 and PTEN) described in BGL may act in concert with KRAS to promote neoplasia. The classical adenoma-carcinoma sequence (with mutations in APC, KRAS, and p53) plays an important role in duodenal carcinogenesis when adenomatous change/dysplasia is present. 19 However, the validity of this paradigm in BG neoplasia is unclear. Of note, BG adenocarcinoma arising from BGH has been associated with GNAS mutations arising in foveolar metaplasia. 20 The BGA presented here did not show dysplasia or metaplasia, and raises a potential role for KRAS in the regulation of BG proliferation, which deserves further studies. 1![Figure 1: Photomicrograph of Brunner gland nodule (H & E x20)](image-2.png "Figure 1 :") 2![Figure 2: Photomicrograph of Brunner gland nodule (H & E x200)](image-3.png "Figure 2 :") K © 2022 Global JournalsBrunner Gland Adenoma with a KRAS G12D Point Mutation * Large Brunner's gland adenoma: Case report and literature review RoccoA doi:10.3748/ wjg.v12.i12.1966 World Journal of Gastroenterology 12 12 1966 2006 * Brunner's glands: A structural, histochemical and pathological profile WJKrause 10.1016/s0079-6336(00)80006-6 Progress in Histochemistry and Cytochemistry 35 4 2000 * Brunner's gland hyperplasia and Hamartoma: Imaging features with Clinicopathologic Correlation NDPatel ADLevy AKMehrotra LHSobin 10.2214/ajr.05.0564 American Journal of Roentgenology 187 3 2006 * Brunner's gland hyperplasia: Treatment of severe diffuse nodular hyperplasia mimicking a malignancy on pancreaticduodenal area WCLee HWYang YJLee 10.3346/jkms.2008.23.3.540 Journal of Korean Medical Science 23 3 540 2008 * Brunner's gland hamartoma of the duodenum: A literature review MZhu HLi YWu 10.1007/s12325-021-01750-6 Advances in Therapy 2021 * Carcinoma arising from Brunner's gland in the duodenum after 17 years of observation -A case report and literature review. Case Reports in Gastroenterology MKoizumi NSata KYoshizawa 10.1159/000108944 2007 1 * A large Brunner's gland hamartoma causing gastrointestinal bleeding and obstruction LcfDe Nes FOuwehand ShaPeters MJBoom doi: 10.1159/ 000111075 Digestive Surgery 24 6 2007 * Malignant potential in a Brunner's gland hamartoma MJBrookes 10.1136/pmj.79.933.416 Postgraduate Medical Journal 79 933 2003 * Gastric foveolar metaplasia with dysplastic changes in Brunner gland hyperplasia TSakurai HSakashita GHonjo 10.1097/01.pas.0000180449.15827.88 The American Journal of Surgical Pathology 29 11 2005 * Juvenile polyposis syndrome LaaBrosens 10.3748/wjg.v17.i44.4839 World Journal of Gastroenterology 17 44 4839 2011 * Loss of LRIG1 leads to expansion of Brunner glands followed by duodenal adenomas with gastric metaplasia YWang CShi YLu EJPoulin 10.1016/j.ajpath.2014.12.014 The American Journal of Pathology 185 4 2015 * Upper and lower gastrointestinal findings in PTEN mutation-positive Cowden syndrome patients participating in an active surveillance program ZLevi HNBaris IKedar 10.1038/ctg.2011.4 Clinical and Translational Gastroenterology 2 11 2011 * Cancer resistance to therapies against the EGFRras-raf pathway: The role of mek EMartinelli FMorgillo TTroiani FCiardiello 10.1016/j.ctrv.2016.12.001 Cancer Treatment Reviews 53 2017 * Not all RAS mutations are equal: A detailed review of the functional diversity of Ras Hot Spot Mutations. Advances in Cancer Research RABurge GAHobbs 10.1016/bs.acr.2021.07.004 2022 * Oncogenic G12D mutation alters local conformations and dynamics of K-Ras SVatansever BErman ZHGümü? 10.1038/s41598-019-48029-z Scientific Reports 9 1 2019 * Powering Precision Medicine through an international consortium GenieAacr Project 10.1158/2159-8290.cd-17-0151 Cancer Discovery 7 8 2017 * Endogenous oncogenic K-RASG12D stimulates proliferation and widespread neoplastic and developmental defects DATuveson ATShaw NAWillis doi: 10.1016/ s1535-6108(04 Cancer Cell 5 4 2004 * The PTEN-PI3K pathway: Of feedbacks and cross-talks ACarracedo PPPandolfi 10.1038/onc.2008.247 Oncogene 27 41 2008 * Signaling cross-talk between TGF-?/BMP and other pathways XGuo X-FWang 10.1038/cr.2008.302 Cell Research 19 1 2008 * Gnasmutated carcinoma arising from gastric foveolar metaplasia in the duodenum after 9 years of observation YMatsuo HYamamoto YSato 10.1007/s12328-018-0856-2 Clinical Journal of Gastroenterology 11 5 2018