Histology of Barrett's esophagus and dysplasia

Review on novel concepts of columnar lined esophagus

BACKGROUND

Columnar lined esophagus (CLE) is a marker for gastroesophageal reflux and associates with an increased cancer risk among those with Barrett's esophagus. Recent studies fostered the development of integrated CLE concepts.

METHODS

Using PubMed, we conducted a review of studies on novel histopathological concepts of nondysplastic CLE.

RESULTS

Two histopathological concepts-the squamo-oxyntic gap (SOG) and the dilated distal esophagus (DDE), currently model our novel understanding of CLE. As a consequence of reflux, SOG interposes between the squamous lined esophagus and the oxyntic mucosa of the proximal stomach. Thus the SOG describes the histopathology of CLE within the tubular esophagus and the DDE, which is known to develop at the cost of a shortened lower esophageal sphincter and foster increased acid gastric reflux. Histopathological studies of the lower end of the esophagus indicate, that the DDE is reflux damaged, dilated, gastric type folds forming esophagus and cannot be differentiated from proximal stomach by endoscopy. While the endoscopically visible squamocolumnar junction (SCJ) defines the proximal limit of the SOG, the assessment of the distal limit requires the histopathology of measured multilevel biopsies. Within the SOG, CLE types distribute along a distinct zonation with intestinal metaplasia (IM; Barrett's esophagus) and/or cardiac mucosa (CM) at the SCJ and oxyntocardiac mucosa (OCM) within the distal portion of the SOG. The zonation follows the pH-gradient across the distal esophagus. Diagnosis of SOG and DDE includes endoscopy, histopathology of measured multi-level biopsies from the distal esophagus, function, and radiologic tests. CM and OCM do not require treatment and are surveilled in 5 year intervals, unless they associate with life quality impairing symptoms, which demand medical or surgical therapy. In the presence of an increased cancer risk profile, it is justified to consider radiofrequency ablation (RFA) of IM within clinical studies in order to prevent the progression to dysplasia and cancer. Dysplasia justifies RFA ± endoscopic resection.

CONCLUSIONS

SOG and DDE represent novel concepts fusing the morphological and functional aspects of CLE. Future studies should examine the impact of SOG and DDE for monitoring and management of gastroesophageal reflux disease (GERD).

Progression of specialized intestinal metaplasia at the cardia to macroscopically evident Barrett's esophagus: an entity of concern in the ProGERD study

OBJECTIVES AND AIMS

Histological Barrett's esophagus, defined as specialized intestinal metaplasia (SIM+) at the cardia without endoscopic suspicion of columnar epithelium, is found frequently in biopsies at the gastro-esophageal junction although its clinical relevance is unknown. The authors aim was to evaluate prospectively the progression of SIM+ to macroscopically evident Barrett's esophagus (BE/SIM+), and to identify risk factors for this progression.

METHODS

Data were obtained from a sub-group of patients (no visible BE at presentation, but SIM+) included in the ProGERD study, a prospective evaluation of the clinical course of GERD under routine clinical care. They had esomeprazole 20-40 mg/day for 2-8 weeks. Symptom assessment was performed annually, and endoscopy with biopsy was planned at baseline, after healing treatment and after 2 and/or 5 years.

RESULTS

128 of 171 (74.8%) patients with unequivocal SIM at the z-line after healing were biopsied again after 2 and/or 5 years. At follow-up, 33 (25.8%) of these patients showed progression to BE/SIM+. Factors significantly associated with progression were smoking, a long history of GERD and severe esophagitis at baseline. Patients who had progressed to BE/SIM+ already at 2 years showed consistent findings at 5 years.

CONCLUSION

More than 20% of GERD patients with SIM+ in this study were found to have BE/SIM+ within 2-5 years. This finding supports the hypothesis that SIM+ at the cardia could be the missing link explaining increased cancer risk in GERD patients without overt BE and merits further investigation in a prospective study.

An analysis of esophagectomy and other techniques in the management of high-grade dysplasia of Barrett's esophagus

Barrett's esophageal (BE) metaplasia is a premalignant condition of the distal esophagus that develops as a consequence of gastroesophageal reflux disease. The progression to carcinogenesis results from progressive dysplastic changes of the metaplastic epithelium through low-grade and then high-grade dysplasia (HGD) to eventually adenocarcinoma of the esophagus. The management of HGD is controversial with proponents for each of the three major management strategies: endoscopic surveillance, endoscopic ablative therapies, and esophagectomy. The aim of the study was to define and discuss the various management strategies of HGD arising from BE metaplasia. There is a paucity of randomized controlled data from which to draw definitive conclusions. All strategies for the management of HGD are reasonable options and are complimentary. BE with HGD is a malignant lesion. A multidisciplinary approach individualizing therapy should be undertaken when possible. Esophageal resection should be reserved for otherwise healthy patients. Endoscopic techniques are viable alternatives to surgery.

Immunoreactivity of cytokeratins 7 and 20 in goblet cells and columnar blue cells in patients with endoscopic evidence of Barrett's esophagus

CONTEXT

Barrett's esophagus is characterized by the presence of goblet cells. However, when alcian-blue is utilized, another type of cells, called columnar blue cells, is frequently present in the distal esophagus of patients with endoscopic evidence of Barrett's esophagus. Cytokeratin 7 and 20 immunoreactivity has been previously studied in areas of intestinal metaplasia at the esophagogastric junction. However, the expression of these cytokeratins in columnar blue cells has not been characterized.

OBJECTIVE

To compare the expression of cytokeratin 7 and 20 in goblet cells and columnar blue cells in patients with endoscopic evidence of Barrett's esophagus.

METHODS

Biopsies from 86 patients with endoscopic evidence of Barrett's esophagus were evaluated. The biopsies were stained for cytokeratin 7 and 20.

RESULTS

Goblet cells were present in 75 cases and columnar blue cells in 50 cases. Overall, cytokeratin 7 expression was similar in goblet cells and columnar blue cells (P = 0.25), while cytokeratin 20 was more common in goblet cells (P <0.001). In individuals with both cell types, however, cytokeratin 7 staining was the same in goblet and columnar blue cells in 95% of the cases, and cytokeratin 20 staining was the same in 77%.

CONCLUSION

Goblet cells and columnar blue cells have similar immunohistochemical staining patterns for cytokeratins 7 and 20 in patients with endoscopic evidence of Barrett's esophagus.

A meta-analysis of the diagnostic accuracy of esophageal capsule endoscopy for Barrett's esophagus in patients with gastroesophageal reflux disease

OBJECTIVES

To evaluate the diagnostic accuracy of esophageal capsule endoscopy (ECE) for Barrett's esophagus (BE) in patients with gastroesophageal reflux disease (GERD).

METHODS

Literature was searched for blinded studies evaluating the diagnostic accuracy of ECE for BE in patients with GERD. Meta-analysis was carried out to calculate pooled sensitivity and specificity of ECE for diagnosis of BE. Subgroup analysis was also carried out based on the reference standard used.

RESULTS

Nine studies comprising a total of 618 patients met the inclusion criteria. The pooled sensitivity and specificity of ECE for the diagnosis of BE for all studies were 77 and 86% respectively. The pooled sensitivity and specificity of ECE for the diagnosis of BE using esophagogastroduodenoscopy (EGD) as the reference standard were 78 and 90%, respectively; using histologically confirmed intestinal metaplasia (IM) as the reference standard pooled sensitivity and specificity were 78 and 73%, respectively. Statistical heterogeneity was not evident among studies for sensitivity results (P=0.270, I(2)=19), but heterogeneity was present for specificity results (P<0.001, I(2)=74). There was no evidence of publication bias. The ECE was found to be safe and had a high rate of patient preference.

CONCLUSIONS

Capsule endoscopy of esophagus has a moderate sensitivity and specificity for the diagnosis of BE in patients with GERD. The EGD remains the modality of choice for evaluation of suspected BE.

Increasing expression of hypoxia-inducible proteins in the Barrett's metaplasia-dysplasia-adenocarcinoma sequence

Hypoxia-associated markers are involved in the progression of several malignancies, but are relatively unstudied in Barrett's carcinogenesis. Our aim was to assess the immunohistochemical expression of hypoxia-inducible factor (HIF)-1α, HIF-2α, erythropoietin (Epo), Epo receptor (Epo-R), Glut-1 and vascular endothelial growth factor (VEGF) along with Ki67/MIB-1 in the Barrett's metaplasia–dysplasia–adenocarcinoma sequence. Endoscopic biopsies of normal squamous epithelium (NSE) (n=20), columnar-lined oesophagus (CLO) (n=15), CLO with intestinal metaplasia (n=20), dysplasia (n=17) and Barrett's type adenocarcinoma (n=20) were obtained. Immunohistochemistry was performed on the paraffin-embedded tissue. A score was calculated for each marker (range 0−300) by multiplying intensity (none 0, weak 1, moderate 2, strong 3) by percentage of expression (range 0–100). Significant increases in the expression of HIF-2α (P=0.014), VEGF (P<0.0001), Epo-R (P<0.0001) and Ki67 (P<0.0001) were found as tissue progressed from NSE to adenocarcinoma. HIF-2α was expressed late in the sequence and was only seen in dysplasia and adenocarcinoma. High HIF-2α expression was seen in 12 out of 20 Barrett's type adenocarcinoma. The late expression of HIF-2α in the Barrett's carcinogenesis sequence and its high expression in adenocarcinoma suggest that it is worth further investigation as a marker of disease progression and therapeutic target.

Characterization of tissue autofluorescence in Barrett's esophagus by confocal fluorescence microscopy

High grade dysplasia and early cancer in Barrett's esophagus can be distinguished in vivo by endoscopic autofluorescence point spectroscopy and imaging from non-dysplastic Barrett's mucosa. We used confocal fluorescence microscopy for ex vivo comparison of autofluorescence in non-dysplastic and dysplastic Barrett's esophagus. Unstained frozen sections were obtained from snap-frozen Barrett's esophagus biopsy samples and scanned with confocal fluorescence microscopy (458 nm excitation; 505-550 nm [green] and > 560 nm [red] emission). Digital micrographs were taken from areas with homogenous and specific histopathology. Visual inspection and statistical analysis were used to evaluate the image datasets. Dysplastic and non-dysplastic Barrett's esophagus epithelia fluoresced mainly in the green spectrum and the main sources of autofluorescence were the cytoplasm and lamina propria. High-grade dysplasia was differentiated from non-dysplastic Barrett's esophagus by microstructural tissue changes. However, there were no specific changes in either the locations or average intensities of intrinsic green and red autofluorescence at the epithelial level that could differentiate between dysplastic and non-dysplastic Barrett's esophagus epithelia, ex vivo. Detectable differences in autofluorescence between BE and dysplasia/cancer in vivo are probably not caused by specific changes in epithelial fluorophores but are likely due to other inherent changes (e.g. mucosal thickening and increased microvascularity) attenuating autofluorescence from the collagen-rich submucosa. Furthermore, confocal fluorescence microscopy provides 'histology-like' imaging of Barrett's tissues and may offer a unique opportunity to exploit microstructural tissue changes occurring during neoplastic transformation for in vivo detection of high-grade dysplasia in Barrett's patients using newly developed confocal fluorescence microendoscopy devices.

Genetics and prevention of oesophageal adenocarcinoma

Gastric cancer has been declining for more than half a century, whereas the incidence of oesophageal cancer is increasing rapidly. The histopathological subtype is also changing with a predominance of oesophageal adenocarcinoma compared with squamous carcinoma. The reasons for these epidemiological changes are not clear, although population-based data have implicated gastro-oesophageal reflux disease as a risk factor. In susceptible individuals reflux of duodeno-gastric contents can lead to the development of a columnar-lined oesophagus, commonly called Barrett's oesophagus. This can then progress to adenocarcinoma via a metaplasia-dysplasia-carcinoma sequence. At the current time, the mortality from oesophageal adenocarcinoma exceeds 80% at 5 years. Therefore, endoscopic surveillance programmes have been generally recommended for patients with Barrett's oesophagus in an attempt to detect early, curable lesions. Unfortunately these programmes are cumbersome and costly and have not yet been proved to reduce population mortality. In order to improve patient outcomes we need to be able to identify patients at high risk and to understand the triggers for disease progression. There is mounting evidence that there is an underlying genetic susceptibility to Barrett's oesophagus and oesophageal adenocarcinoma. However, this is likely to be as a result of multiple low penetrance susceptibility genes which have yet to be identified. Once patients are identified as having Barrett's oesophagus their chance for developing adenocarcinoma is in the order of 0.5%-1% per year. The histological assessment of dysplasia as a predictor of cancer development is highly subjective. Therefore multiple, specific somatic mutations in the tissue have been investigated as potential biomarkers. The most promising markers to date are the presence of aneuploidy, loss of heterozygosity of p53 and cyclin D1 overexpression. However, a study of evolutionary relationships suggest that mutations occur in no obligate order. Combinatorial approaches are therefore being advocated which include genomic profiling or the use of a panel of molecular markers in order to define the common molecular signatures that can then be used to predict malignant progression. An alternative approach would be to use markers for the final common pathway following genetic instability, which is the loss of proliferative control. We have demonstrated an increase in the expression of a novel proliferation marker, Mcm2, which occurs during the malignant progression of Barrett's oesophagus. These Mcm2-expressing cells are detectable on the surface, and hence a cytological approach may be applicable. In view of the role of reflux components in the pathogenesis of Barrett's oesophagus the effect of acid and bile on the cell phenotype have been studied. These studies have demonstrated that pulsatile acid and bile exposure induce cell proliferation. The mechanism for the hyperproliferative response appears to involve p38 mitogen activated protein kinase (MAPK) pathways as well as protein kinase C (PKC) and cyclo-oxygenases. A clinical implication of the laboratory studies is that suppression of acid and bile may need to be profound in order to suppress cell proliferation and, by inference, ultimately prevent the development of dysplasia. There is some support for this concept from short-term clinical studies, and a large randomised chemoprevention trial is being instigated which will evaluate the effect of proton pump inhibitors with or without aspirin. Given the epidemic increase in oesophageal adenocarcinoma and the dismal 5-year mortality rate, a radical approach is necessary to prevent cancer development in individuals with pre-malignant lesions.

The metabolic marker tumour pyruvate kinase type M2 (tumour M2-PK) shows increased expression along the metaplasia-dysplasia-adenocarcinoma sequence in Barrett's oesophagus

BACKGROUND

Proliferating and tumour cells express the glycolytic isoenzyme, pyruvate kinase type M2 (M2-PK). In tumours cells, M2-PK usually exists in dimeric form (tumour M2-PK), causing the accumulation of glycolytic phosphometabolites, which allows cells to invade areas with low oxygen and glucose concentrations.

AIMS

To investigate the expression of tumour M2-PK during the metaplasia-dysplasia-adenocarcinoma sequence of Barrett's oesophagus, and to assess the prognostic usefulness of tumour M2-PK in oesophageal cancer.

MATERIALS/METHODS

One hundred and ninety cases selected from the histopathology archives as follows: 17 reflux oesophagitis, 37 Barrett's oesophagus, 21 high grade dysplasia, 112 adenocarcinomas, and three control tumours. Sections were stained immunohistochemically with antibody to tumour M2-PK.

RESULTS

Tumour M2-PK was expressed in all cases, and increased cytoplasmic expression was seen with progression along the metaplasia-dysplasia-adenocarcinoma sequence. All cases of adenocarcinoma showed 100% staining so that tumour M2-PK was not a useful prognostic marker.

CONCLUSIONS

Tumour M2-PK is not a specific marker of Barrett's adenocarcinoma, but may be important as a marker of transformed and highly proliferating clones during progression along the metaplasia-dysplasia-adenocarcinoma sequence.