Serrated adenoma of the duodenum

A spatial expression atlas of the adult human proximal small intestine

The mouse small intestine shows profound variability in gene expression along the crypt-villus axis1,2. Whether similar spatial heterogeneity exists in the adult human gut remains unclear. Here we use spatial transcriptomics, spatial proteomics and single-molecule fluorescence in situ hybridization to reconstruct a comprehensive spatial expression atlas of the adult human proximal small intestine. We describe zonated expression and cell type representation for epithelial, mesenchymal and immune cell types. We find that migrating enterocytes switch from lipid droplet assembly and iron uptake at the villus bottom to chylomicron biosynthesis and iron release at the tip. Villus tip cells are pro-immunogenic, recruiting γδ T cells and macrophages to the tip, in contrast to their immunosuppressive roles in mouse. We also show that the human small intestine contains abundant serrated and branched villi that are enriched at the tops of circular folds. Our study presents a detailed resource for understanding the biology of the adult human small intestine.

Traditional Serrated Adenoma of the Gallbladder, a Case Report

While overwhelming majority of laparoscopic cholecystectomy specimens performed for gallstones or cholecystitis show rather typical findings, sometimes polypoid structures are also removed. These can be related to cholesterolosis or conventional adenomas, but occasionally extraordinary findings do emerge. In our case, a 67-year old lady with typical complaints of cholecystitis underwent routine laparoscopic cholecystectomy. Preoperative ultrasound revealed a polypoid mass with inflammation and without suspicion for malignancy. Microscopic examination showed partly conventional, low-grade dysplastic crypts forming a villous and rather complex structure. Ectopic crypt foci, slit-like serration pattern and serrated dysplasia with eosinophylic cytoplasm and centrally located nuclei were seen throughout the lesion, thus a traditional serrated adenoma (TSA) of the gallbladder was diagnosed. TSA represents the rarest subtype of serrated lesions in the colon and extracolonic manifestations are sporadically reported. Until now only a single case of a serrated adenoma was reported from the gallbladder. Here we describe the detailed clinical, pathological and molecular findings of our case and discuss these in the light of current literature data regarding this field.

Familial Adenomatous Polyposis-associated Traditional Serrated Adenoma of the Small Intestine: A Clinicopathologic and Molecular Analysis

Familial adenomatous polyposis (FAP) is an inherited cancer predisposition syndrome associated with numerous gastrointestinal tract adenomatous polyps, as well as gastric fundic gland polyps and pyloric gland adenomas in the upper gastrointestinal tract. While colonic FAP-associated traditional serrated adenomas (TSAs) have been reported in a few studies, small bowel FAP-associated adenomas with TSA morphology have not been characterized. This study describes the clinicopathologic and molecular findings of this type of adenoma in the small bowel of patients with FAP. We reviewed small bowel adenomas in 45 consecutive FAP patients to identify adenomas with zones showing slit-like serrations, cells with eosinophilic cytoplasm, ectopic crypt formation, and vesicular nuclei. Sporadic small bowel adenomas from 51 consecutive patients were also reviewed for adenomas with the same features. Of the 177 polyps from 45 FAP patients and 60 polyps from 51 nonsyndromic patients, 18 TSAs from 9 FAP patients (20%) and 10 TSAs from the sporadic group (19.6%) were identified. FAP patients presented at a younger age than nonsyndromic patients (median: 43 vs. 66; P=0.0048). FAP-associated TSAs were asymptomatic and smaller than sporadic TSAs (median size: 0.6 vs. 2.5 cm; P=0.00006). Immunostaining for β-catenin and testing for BRAF and KRAS mutations were performed in a subset of the cohort. Nuclear β-catenin was seen in 1 FAP-associated TSA and 3 nonsyndromic TSAs. All TSAs (FAP-associated and nonsyndromic) showed wild-type BRAF, while KRAS mutations were identified only in the nonsyndromic setting. In summary, small bowel FAP-associated and sporadic TSAs share a similar morphology, and the BRAF-serrated pathway does not contribute to their pathogenesis.

First case of serrated lesion of the duodenal papilla in a patient with serrated colonic polyposis

A serrated polyposis syndrome was diagnosed in a 26-year-old female presenting with gastrointestinal symptoms. Screening for other lesions of the gastrointestinal tract showed a serpiginous looking papilla, described as possibly dysplastic. Histological analysis of biopsies showed a serrated lesion. This case describes the first known association between a duodenal serrated lesion and serrated polyposis syndrome. Upper GI screening is probably of little interest in this setting. In patients with upper GI serrated lesions, we recommend screening colonoscopy.

Small Bowel Epithelial Precursor Lesions: A Focus on Molecular Alterations

The wider use of gastrointestinal endoscopic procedures has led to an increased detection of small intestinal preneoplastic and neoplastic epithelial lesions, most of which are identified in the duodenum and ampullary region. Like their malignant counterparts, small intestinal glandular precursor lesions, which include adenomas and hamartomas, may arise sporadically or be associated with hereditary tumor syndromes, such as familial adenomatous polyposis, MUTYH-associated polyposis, Lynch syndrome, Peutz-Jeghers syndrome, juvenile polyposis syndrome, and Cowden syndrome. In addition, dysplastic, preinvasive lesions have been observed adjacent to small bowel adenocarcinomas complicating immune-related disorders, such as celiac or Crohn’s disease. Adenomatous lesions may exhibit an intestinal-type, gastric-type, or, very rarely, serrated differentiation, related to different molecular pathogenetic mechanisms. Finally, in the background of multiple endocrine neoplasia 1 syndrome, precursor neuroendocrine growths have been described. In this review we offer a comprehensive description on the histo-molecular features of the main histotypes of small bowel epithelial precursors lesions, including: (i) sporadic adenomas (intestinal-type and gastric-type; non-ampullary and ampullary); (ii) syndromic adenomas; (iii) small bowel dysplasia in celiac and Crohn’s disease; (iv) serrated lesions; (v) hamartomatous lesions; and (vi) neuroendocrine precursor lesions.

Gastric and small intestinal traditional serrated adenomas: a detailed morphologic and immunohistochemical analysis

BACKGROUND/AIMS

Traditional serrated adenomas (TSAs), despite their low incidence in colorectum, may originate in other parts of the gastrointestinal (GI) tract, including stomach and small intestine. Malignant transformation for upper GI TSAs has recently been reported in the literature. Here, we present a series of gastric and small intestinal TSAs with the aim to characterize their morphologic and immunophenotypic features as well as their neoplastic potential in a compartmental manner using digitalized images.

MATERIALS AND METHODS

The study comprised 12 GI polyps with TSA features-5 gastric and 7 small intestinal. The extent of the characteristic features of TSA, including eosinophilic cells, ectopic crypt foci (ECF), slit-like serration, foveolar epithelium, goblet cells, together with dysplastic-carcinomatous foci were assessed on digitalized H-E images and were used as reference for immunohistochemical analysis.

RESULTS

All polyps in the cohort contained eosinophilic cells as the most extensive morphologic feature followed by ECF and slit-like serration in decreasing order. Serrated dysplasia was more common in gastric polyps, which more frequently showed neoplastic progression compared with the intestinal ones. CK20 was the most widely expressed marker with a preference to eosinophilic cells while ECFs were mostly negative. Ki67 showed the opposite pattern of CK20. MUC6 and MUC2 were selectively expressed in the basal zone and goblet cells, respectively.

CONCLUSION

Our results showed that the presence of eosinophilic cells with pencillate nuclei commonly accompanied by ECF and slit-like serration are the defining features of gastric and small intestinal TSAs. They frequently harbor neoplastic foci, particularly in gastric location where serrated dysplasia seems to be more common.

Duodenal Epithelial Polyps: A Clinicopathologic Review

CONTEXT.—

Duodenal epithelial polyps are reported in 1.5% to 3% of individuals referred for upper endoscopy. Most duodenal epithelial polyps are asymptomatic and nonneoplastic; however, a small subset is neoplastic and may progress to adenocarcinoma. Recent advances in immunohistochemical and molecular techniques have helped further characterize these polyps, shedding light on their origin, classification, and risk of progression to adenocarcinoma.

OBJECTIVE.—

To provide a comprehensive clinicopathologic review of nonneoplastic and neoplastic duodenal epithelial polyps, with particular emphasis on recent developments in classification schemes and risk stratification based upon immunohistochemical and molecular profiles.

DATA SOURCES.—

This review is based on peer-reviewed literature and the authors' experiences.

CONCLUSIONS.—

In this review we provide an update on the clinicopathologic, immunohistochemical, and molecular features of duodenal epithelial polyps and discuss the surveillance recommendations and treatment options available. Particular attention should be placed on recognizing duodenal adenomas with intestinal, gastric, and serrated phenotype, as they have an increased risk of malignant transformation if not completely excised.

Jejunal Serrated Adenoma Diagnosed and Treated by Double-Balloon Enteroscopy

Serrated polyps are most commonly located in the colorectum and have been well recognized as an important precursor lesion for colorectal cancer. Serrated adenoma in the small intestine has been reported more rarely but may represent a distinct morphological and biological subtype with malignant potential. Here, we present the case of a 65-year-old female who underwent double-balloon enteroscopy due to obscure gastrointestinal bleeding. A polyp sized 3.5 × 2.0 cm with a long pedicle in the jejunum, located 50 cm distal to the Treitz ligament, was detected. Endoscopic mucosal resection was done. The pathological results revealed a traditional serrated adenoma sized 3.5 × 2.2 cm.

Clinical features of upper gastrointestinal serrated lesions: An endoscopy database analysis of 98746 patients

AIM

To analyse the clinical features of patients with the serrated lesions in the upper gastrointestinal tract (UPGI) tract.

METHODS

Patients who underwent routine esophagogastroduodenoscopy (EGD) at the Digestive Endoscopy Centre of General Hospital, Tianjin Medical University between January 2011 and December 2015 were consecutively recruited. Patients with UPGI serrated lesions were consecutively identified. The patients’ demographics and histopathology were recorded. The colorectal findings for patients who underwent colonoscopy simultaneously or within six months were also extracted from the colonoscopy database. In addition, we analysed differences in colorectal neoplasia detection between the study patients and randomly selected patients matched for age and gender who did not exhibit serrated lesions and who also underwent colonoscopy in the same period.

RESULTS

A total of 21 patients out of 98746 patients (0.02%) who underwent EGD were confirmed to have serrated lesions with predominantly crenated, sawtooth-like configurations. The mean age of the 21 patients was (55.3 ± 17.2) years, and 11 patients were male (52.4%). In terms of the locations of the serrated lesions, 17 were found in the stomach (including 3 in the cardia, 9 in the corpus and 5 in the antrum), 3 were found in the duodenum, and 1 was found in the esophagus. Serrated lesions were found in different mucosal lesions, with 14 lesions were detected in polyps (8 hyperplastic polyps and 6 serrated adenomas with low grade dysplasia), 3 detected in Ménétrier gastropathy, 3 detected in an area of inflammation or ulcer, and 1 detected in the intramucosal carcinoma of the duodenum. In addition, colonoscopy data were available for 18 patients, and a significantly higher colorectal adenoma detection rate was observed in the UPGI serrated lesions group than in the randomly selected age- and gender-matched group without serrated lesions who also underwent colonoscopy in the same period (38.9% vs 11.1%, OR = 5.091, 95%CI: 1.534-16.890, P = 0.010). The detection rate of advanced adenoma was also higher in the UPGI serrated lesions group (22.2% vs 4.2%, OR = 6.571, 95%CI: 1.322-32.660, P = 0.028).

CONCLUSION

Serrated lesions in the UPGI were detected in various mucosal lesions with different pathological morphologies. Moreover colonoscopy is recommended for the detection of concurrent colorectal adenoma for these patients.

Slow-Growing Early Adenocarcinoma Arising from Traditional Serrated Adenoma in the Duodenum

Serrated polyps are classified into 3 distinct types: hyperplastic polyp, sessile serrated adenoma, or transitional serrated adenoma. A serrated adenoma is a precursor lesion for colorectal carcinoma. Serrated polyps are commonly found in the colorectum but have rarely been described in other parts of the gastrointestinal tract. Serrated adenomas in the small intestine may represent aggressive lesions with high malignant potential, according to some reports. A 66-year-old man with no significant medical history underwent esophagogastroduodenoscopy (EGD) for general examination. He had a 1-cm sized, Yamada type IV polyp, with focal white patch in the second portion of the duodenum. The biopsy result revealed gastric metaplasia and chronic inflammation. He wanted regular follow -up examinations. The follow-up EGDs were done every year. There were no changes in the shape and size of the polyp. The pathologic findings were unchanged. Then, he underwent EGD for general medical check-up again 5 years after the first detection. The size of the polyp was slightly increased. The biopsy result revealed serrated polyp, unclassified. Endoscopic mucosal resection was done. The pathologic result revealed a 0.8 × 0.5-cm sized, well differentiated tubular adenocarcinoma. Carcinomas are multifocally spread on the traditional serrated adenoma, and the proportion of the adenocarcinoma component is approximately 50%. The tumor had invaded the lamina propria but confined to the mucosa. The resection margins were negative, and no lymphovascular invasion or perineural invasion was seen. Abdominal pelvic computed tomography and positron emission tomography showed no other solid organ involvement or metastasis. Surveillance follow-up EGDs were done after 3 months and 1 year. There was no evidence of recurrence.

Traditional serrated adenomas of the upper digestive tract

For many years, it was generally accepted that the vast majority of the colorectal carcinomas (CRCs) evolved from conventional adenomas, via the adenoma–carcinoma sequence. More recently, serrated colorectal polyps (hyperplastic polyps, sessile serrated polyps and traditional serrated adenomas (TSAs)) have emerged as an alternative pathway of colorectal carcinogenesis. It has been estimated that about 30% of the CRC progress via the serrated pathway. Recently, TSAs were also detected in the upper digestive tract. In this work, we review the literature on TSA in the oesophagus, the stomach, the duodenum, the pancreatic main duct and the gallbladder. The review indicated that 53.4% (n=39) out of the 73 TSA of the upper digestive tract now in record showed a simultaneously growing invasive carcinoma. As a corollary, TSAs of the upper digestive tract are aggressive adenomas that should be radically excised, either endoscopically or surgically, to rule out the possibility of a synchronously growing invasive adenocarcinoma or to prevent cancer progression. The present findings substantiate a TSA pathway of carcinogenesis in the upper digestive tract.

Do serrated neoplasms of the small intestine represent a distinct entity? Pathological findings and molecular alterations in a series of 13 cases

AIMS

To characterize pathological, immunohistochemical and molecular features of small intestinal serrated neoplasms.

METHODS AND RESULTS

We report 13 serrated neoplasms located predominantly in the duodenum (median age, 71 years; male to female ratio, 7:6). The serrated adenomas demonstrated prominent serration, ectopic crypt formations and cytological features reminiscent of colorectal traditional serrated adenomas. Almost half the serrated adenomas demonstrated high-grade dysplasia or were associated with an adenocarcinoma. Immunohistochemical and molecular analysis showed an intestinal (CDX2-positive) phenotype in all tumours, abnormal β-catenin staining in three cases (23%), abnormal p53 expression in four cases (31%), focal loss of MGMT expression in one case (8%), KRAS mutation in five cases (38%) and CpG island methylator phenotype in six cases (50%). A diffuse pattern of Ki67 expression was present in eight adenomas (62%) and was associated with high-grade dysplasia (P = 0.02). No BRAF(V600E) mutation or loss of MLH1 expression was observed.

CONCLUSIONS

To our knowledge, this is the first series reporting serrated adenoma in the small intestine, a rare subtype of adenomas resembling traditional serrated adenoma with aggressive morphological features. The absence of the BRAF(V600E) mutation does not support a role for the serrated neoplasia pathway in the development of these lesions, as in colorectal serrated polyps.

[Serrated polyps of the duodenum. Three cases with immunohistological and molecular pathological findings]

We report on three cases of serrated polyps of the duodenum which were incidental endoscopic findings in three male patients with a median age of 70 years (range 63-84 years). Architecturally the histological findings in cases 1 and 2 were similar to hyperplastic polyps of the colon. In case 3 there was a low grade intraepithelial neoplasia which covered the whole polyp. This polyp relapsed after 2 years with similar histological findings. Immunohistochemically an increased proliferative activity was found in case 3 as well as associated overexpression of p16 (INK4a) and p53. No abnormal expression of MLH1 and β-catenin was found in any of the polyps. Molecular pathological analysis showed a BRAF mutation (V600E) in case 3. A wild type sequence in the KRAS gene was found in all polyps. In conclusion, serrated polyps should be included in the diagnostic spectrum of benign duodenal polyps.

Serrated adenoma of the stomach: Case report and literature review

Gastric serrated adenomas are histologically characterized by protruding glands with lateral saw tooth-like indentations lined with stratified dysplastic cells containing abundant eosinophilic cytoplasm. Since the first case of gastric serrated adenoma found in 2001, 18 additional cases have been reported. Gastric serrated adenomas have a particular proclivity to progress to invasive carcinoma; 75% or 15 of the 20 cases now in record - including the present one - exhibited invasive carcinoma. The 20(th) case of gastric serrated adenoma reported here differs from the preceding ones in as much as it evolved in a patient with Lynch syndrome, implying that this adenoma phenotype may develop not only sporadically but also in patients with hereditary traits.

Hyperplastic polyp of the duodenum: a report of 9 cases with immunohistochemical and molecular findings

Benign serrated polyps are commonly found in the colorectum but have rarely been described in other parts of the gastrointestinal tract. We report a series of 9 serrated polyps arising in the duodenum with clinicopathologic features, immunohistochemical expression profile of mucins (MUC2, MUC5AC, MUC6), and molecular analysis for BRAF and KRAS. The polyps were diagnosed as incidental endoscopy findings in 9 different patients, comprising 3 male and 6 female patients, with a mean age of 52.2 years (range, 21-72 years). The second part of the duodenum was the most common site (n = 5), followed by the ampulla (n = 1) and the distal duodenum (n = 1), with the location of the 2 remaining polyps unspecified. Other upper gastrointestinal tract pathology features included Barrett esophagus for 5 patients, Helicobacter gastritis for 1 patient, and mild chronic gastritis for 1 patient. The histologic appearance of the polyps was similar to microvesicular hyperplastic polyp in the colorectum. Immunostaining for mucins showed MUC6 expression in the crypt bases of all polyps, MUC5AC expression in 8 cases (89%), and mucin 2 expression in 6 cases (67%). Molecular testing was successful in 6 polyps, showing BRAF mutation (V600E) in 2 polyps, KRAS mutation in 2 polyps, and no mutation for either gene in 2 polyps. Colonoscopy reports were available for 6 patients, of whom 4 were diagnosed with hyperplastic polyps or sessile serrated polyps in the colorectum. However, no patient met the criteria for serrated polyposis. Although probably rare and of uncertain malignant potential, hyperplastic polyp should be considered in the differential diagnosis of benign duodenal polyp.

Evaluation of non-ampullary duodenal polyps: Comparison of non-neoplastic and neoplastic lesions

AIM: To evaluate duodenal polyps, divided into non-neoplastic and neoplastic lesions. In addition, the clinical characteristics of duodenal hyperplastic polyps are determined.

METHODS: We analyzed medical records of 50 114 consecutive patients submitted to for first diagnostic esophago-gastroduodenoscopy between January 2004 and December 2009. We excluded lesions on the ampulla of Vater and submucosal tumors. We studied 510 cases that were diagnosed endoscopically with duodenal polyps and enrolled a total of 221 cases that had undergone tissue biopsy. We analyzed the differences between non-neoplastic and neoplastic lesions, and determined the clinical features of duodenal hyperplastic polyps.

RESULTS: Non-neoplastic lesions were found in 196 patients and neoplastic lesions in 25 patients. On univariate analysis, there were significant differences in shape, location, and size. Polyps more than 10 mm in diameter or polyps in the second portion had independent risk factors for being neoplastic lesions, as identified by multivariate analysis. In 23 cases of hyperplastic polyps (79.3%), they were accompanied by gastro-duodenal pathology, which was possibly associated with Helicobacter pylori.

CONCLUSION: Polyps of more than 10 mm or polyps in the second portion of the duodenum should be evaluated by histological examination.

Stem cells might participate in the cell turnover of duodenal adenomas

Eighty-three duodenal adenomas were stained with hematoxylin-eosin (H&E) and with anti-lysozyme immunostain. Mature Paneth cells were those showing coarse brightly red cytoplasmic granules in H&E stain and Paneth cell precursors were those lysozyme-expressing cells that had remained undetected in H&E stain. In the adenomas, the number of mature Paneth cells/high power field varied from 4 to 12 (mean 6.5) in H&E stain, and of lysozyme-expressing cells from 32 to 62 (mean 46.5) (p<0.05). Lysozyme-expressing cells were found haphazardly distributed within the histological profile of the lesion, even in the most superficial cell layer of the dysplastic glands. The latter suggests that if the innate programmed vector of cell migration were valid for duodenal adenomas (from stem cells towards the bottom of the crypts for Paneth cells) the stem cells, normally overlaying Paneth cells, would have been exfoliated into the lumen. Another, less likely option, is that mutated stem cells at the bottom of duodenal adenomas translocate, in an unprecedented manner, the ontogenic signals of migration for Paneth cells. This stochastic molecular option would imply a total reversal of the normal migratory vector for Paneth cells, to a more aberrant, paradoxical migration flow, from stem cells to the villus domain, before exfoliation. Because of the unique migratory direction of the Paneth cells in the crypts of Lieberkühn, the duodenal adenoma emerges as a suitable histo-biological model to monitor the fate of stem cells. It is suggested that stem cells, together with the other recordable mature cells, namely dysplastic enterocytes, Paneth cells and goblet cells, participate in the cell turnover of duodenal adenomas. Further studies are necessary to definitively validate the abovementioned suggested hypothesis.

Hyperplastic polyps of the duodenum: an unusual histological finding

A 58-year-old man underwent upper gastrointestinal surveillance endoscopy for Barrett's oesophagus. This showed a possible gastric ulcer, although histological examination was normal. Follow-up endoscopy showed white ridges in the distal duodenum and these were subjected to biopsy. Histological examination of the biopsy specimens showed polypoid duodenal mucosa showing features similar to those of a hyperplastic polyp of the colon. In addition, the mucosal surface was focally of gastric surface type. The features were interpreted overall as most likely to represent an unusual form of regenerative change in the setting of previous chronic inflammatory mucosal damage. The case is presented as an unusual histological phenomenon at this site; it would be important not to overdiagnose neoplasia in this situation.

Gastric duodenal metaplasia in duodenal adenomas

BACKGROUND

In cases of known aetiology, gastric duodenal metaplasia (GMD) is a reversible lesion. In cases of unknown aetiology, the fate of GMD remains elusive. GMD was recently found in a duodenal adenoma.

AIM

To audit the frequency of GMD occurring in a cohort of duodenal adenomas.

METHODS

Filed H&E-stained sections from 306 consecutive duodenal adenomas were investigated for the presence of GMD.

RESULTS

68% of the adenomas (n = 208) were from patients with familial adenomatous polyposis (FAP), and the remaining 32% (n = 98) were sporadic. GMD was found in 31.7% (66/208) of the duodenal FAP adenomas and in 59.2% (58/98) of the duodenal sporadic adenomas (p<0.05). The causes for this difference are elusive.

CONCLUSIONS

As for other metaplasias of the gastrointestinal tract (intestinal metaplasia of the oesophagus and of the stomach, and metaplastic-hyperplastic polyposis of the colon, known to antedate neoplastic transformation), a subset of GMDs of unknown cause might be present in the duodenal mucosa before adenomatous changes ensue. That subset of GMD might have neoplastic proclivity similar to the metaplastic epithelium in other organs of the gastrointestinal tract. The known carcinogenic effect of high concentrations of bile acids and pancreatic juices bathing the duodenal mucosa carrying an irreversible subset of GDM might set aflame the adenomatous neoplastic transformation in these patients.

Gastric duodenal metaplasia in duodenal adenomas

BACKGROUND

In cases of known aetiology, gastric duodenal metaplasia (GMD) is a reversible lesion. In cases of unknown aetiology, the fate of GMD remains elusive. GMD was recently found in a duodenal adenoma.

AIM

To audit the frequency of GMD occurring in a cohort of duodenal adenomas.

METHODS

Filed H&E-stained sections from 306 consecutive duodenal adenomas were investigated for the presence of GMD.

RESULTS

68% of the adenomas (n = 208) were from patients with familial adenomatous polyposis (FAP), and the remaining 32% (n = 98) were sporadic. GMD was found in 31.7% (66/208) of the duodenal FAP adenomas and in 59.2% (58/98) of the duodenal sporadic adenomas (p<0.05). The causes for this difference are elusive.

CONCLUSIONS

As for other metaplasias of the gastrointestinal tract (intestinal metaplasia of the oesophagus and of the stomach, and metaplastic-hyperplastic polyposis of the colon, known to antedate neoplastic transformation), a subset of GMDs of unknown cause might be present in the duodenal mucosa before adenomatous changes ensue. That subset of GMD might have neoplastic proclivity similar to the metaplastic epithelium in other organs of the gastrointestinal tract. The known carcinogenic effect of high concentrations of bile acids and pancreatic juices bathing the duodenal mucosa carrying an irreversible subset of GDM might set aflame the adenomatous neoplastic transformation in these patients.

[Serrated neoplasia of the gastro-intestinal tract]

Serrated neoplasia of the gastro-intestinal tract have peculiar microscopic and molecular features that are still incompletely described. Some serrated polyps seem to be involved in a new carcinogenic pathway in the colon: the serrated neoplasia pathway, with hypermethylation of the cytosine-guanine dinucleotides, located in the promoter of some genes such as h-MLH1, BRAF and MGMT. The natural history of the serrated polyps and their risk for progression to malignancy are still unclear. There is no official guideline for the management of serrated polyps. The aim of this article is to describe the epidemiological, morphological, immunohistochemical and molecular characteristics of the serrated neoplasia of the gastrointestinal tract: hyperplastic polyps, "traditional" serrated adenomas, mixed hyperplastic and adenomatous polyps, sessile serrated adenomas, hyperplastic polyposis and serrated adenocarcinomas.