A reappraisal of brush cytology for screening of Barrett’s esophagus

Barrett’s esophagus is defined as a condition in which normal squamous epithelium of the distal esophagus is replaced by incomplete intestinalized columnar epithelium [1]. This change of the metaplastic esophageal epithelium to a columnar type of epithelium is viewed as a complication of excessive esophageal mucosal damage caused by symptomatic or asymptomatic gastroesophageal reflux disease (GERD) [2] [3]. It is appreciated that generally a subset of patients with severe reflux-induced esophagitis develops metaplastic columnar epithelium and even a smaller group of these patients eventually develop dysplasia, and finally, at the top of the large iceberg, a very small number would go on to develop high grade dysplasia or esophageal adenocarcinoma (EAC). The most common risk factor for EAC is chronic GERD, which is associated with an approximately 16-fold increased risk of developing EAC, and occurs in as many as 60 % of patients in whom this tumor is diagnosed. The risk of developing EAC in patients with Barrett’s esophagus appears to be approximately 30 – 125-fold greater than that in the general population, with an estimated incidence of 1 in 18 patient years [2] [3].

Current management strategies for patients with Barrett’s esophagus include frequent endoscopic surveillance with multiple biopsies, but these procedures have limitations. Many clinicians still believe that endoscopic esophageal biopsy of the lower esophagus is the “gold standard” for a diagnosis of Barrett’s esophagus [4]. Progression of Barrett’s to EAC is characterized by histopathological changes, classified as low grade (LGD) and high grade dysplasia (HGD). Routine surveillance programs for patients with Barrett’s esophagus aim at screening for these histological changes [4]. However, as dysplasia is often focal, sampling errors may confound the correct diagnosis. Epithelial dysplasia or even early carcinoma may visually not be apparent to the endoscopist, and may be missed when taking random biopsies. Thus, screening for histological changes alone is not efficient, nor reliable, for identifying Barrett’s patients at risk [5]. Of importance is that progression of Barrett’s esophagus to EAC is associated with the occurrence of several genetic changes. It is anticipated that these molecular changes may serve as biomarkers, the assessment of which may lead to an improvement in the efficiency of current screening programs [5] [6].

Cytological studies have potential advantages over endoscopic biopsy for diagnosing Barrett’s esophagus and monitoring for dysplasia. Some of the named advantages of cytology include the ability to sample a greater area of involved epithelium, preferential exfoliation of the less cohesive dysplastic cells, simplicity, and lower cost compared with endoscopy with biopsy [1]. The recently developed “Cytosponge”, by Dr R. Fitzgerald’s group, which is currently being applied in the Barrett’s Esophagus Screening Trial (BEST) in the UK, can even be used to obtain esophageal brush specimens without performing endoscopy. The downside of cytological specimen study is that it requires specific cytopathological expertise and experience, which is only available in a limited number of expert centers.

In the study by Kumaravel et al., cytology was found to have a good sensitivity for the detection of adenocarcinoma and high grade dysplasia, and good specificity for the detection of intestinal metaplasia without dysplasia but poor sensitivity for the detection of low grade dysplasia [7]. In this study the concordance rate between cytology and histology was found to be 80 %. The sensitivity of cytology for any dysplasia was 49 %, and specificity was 95 %. However, sensitivity was 82 % for high grade dysplasia/adenocarcinoma but only 31 % for low grade/indefinite for dysplasia. Previous studies have described a concordance rate of 72 % between cytology and histology [8]. Studies to date have reported a sensitivity for detection of high grade dysplasia or adenocarcinoma ranging from 89 % to 100 % [4] [9] [10] [11] [12]. Sensitivity for low grade dysplasia has been reported in only a few studies [4] [13]. Saad et al., reported a sensitivity of 20 % for the detection of low grade dysplasia, but their study included a large number of patients with a variety of benign lesions of the esophagus that were different from Barrett’s esophagus [4]. Taking histology as the gold standard, cytology seems to have a rather poor accuracy for diagnosing low grade dysplasia. Yet, we need to consider that histological criteria by itself, in particular for the diagnosis of low grade dysplasia, have high intra- and interobserver variation [5]. High grade dysplasia or adenocarcinoma seems to develop in approximately 10 % – 28 % of patients with low grade dysplasia. As prospective long-term follow-up studies comparing cytology and histology diagnosis in predicting progression are lacking, it is not clear which of these criteria is superior in the detection of cases at risk for progression. If cytology is going to be reappraised as a method for screening Barrett’s esophagus, this needs to be further investigated in future follow-up studies.

One other important aspect of brush cytology is that it also provides an excellent source of material for the study of molecular genetic abnormalities. In the isolated cells obtained in the brush specimens, techniques such as DNA fluorescence in situ hybridization (FISH) for the assessment of genetic abnormalities can be easily applied. FISH is a rapid technique that allows the determination of the numeric complement of entire chromosomes, as well as gains or losses of specific genetic regions in conjunction with cellular morphology. It can be applied to both fresh and archival cytology specimens [13] [14] [15]. Brush cytology has been shown to have good sensitivity for the detection of adenocarcinoma and high grade dysplasia, good specificity for the detection of intestinal metaplasia without dysplasia, and may even detect abnormalities missed in biopsy specimens. However, problems are encountered with the cytological detection of low grade dysplasia [11] [13]. For cytology to become a useful surveillance option, its sensitivity for detecting cases at increased risk should be improved. This might be accomplished by adding biomarkers to routine cytology preparations to define patients at increased risk of progression to cancer. Numerous biological biomarkers that may potentially define patients at increased risk for developing EAC have been published [3] [15] [16] [17]. Among the most frequently and most thoroughly investigated molecular changes preceding the development of adenocarcinoma in Barrett’s esophagus are alterations in p53 (mutation, deletion, or loss of heterozygosity [LOH]), p16 (mutation, deletion, promoter hypermethylation, or LOH), and aneuploidy by flow cytometry [1] [3].

Multicolor DNA FISH on cytology specimens can potentially assess losses of these genes and ploidy changes even in a single assay [15] [16]. Future evaluation of this combined methodology in long-term prospective follow-up studies of Barrett cohorts are pending.

To conclude, cytology has excellent specificity, good sensitivity for the detection of high grade dysplasia/adenocarcinoma but poor sensitivity for low grade dysplasia. There is substantial concordance between cytology and histology for the detection of dysplasia. However, the accuracy of cytology alone in predicting future development of adenocarcinoma is unknown. Combining biomarkers on cytology specimens is highly promising and might become a powerful screening tool in the surveillance of Barrett’s esophagus.

Competing interests: None

References

• 1 Fahmy M, Skacel M, Gramlich T. et al . Chromosomal gains and genomic loss of p53 and p16 genes in Barrett’s esophagus detected by flourescence in situ hybridization of cytology specimens.  Modern Pathology. 2004;  17 588-596
• 2 Zagorowicz E, Jankowski J. Molecular changes in the progression of Barrett’s oesophagus. Systematic review of molecular biomarkers, regarding the ASPECT study in the UK.  Post Grad Med J. 2007;  83 529-535
• 3 Tischoff I, Tannapfel A. Barrett’s esophagus: can biomarkers predict progression to malignancy?.  Expert Rev Gastroenterol Hepatol. 2008;  2 653-663
• 4 Saad S R, Mahood K L, Clary M K. et al . Role of cytology in the diagnosis of Barretts esophagus and associated neoplasia.  Diagn Cytopathol. 2003;  29 130-135
• 5 Huang Q, Hardie L J. Biomarkers in Barrett’s oesophagus.  Biochemical Society Transaction. 2010;  38 343-347
• 6 Spechler S J. Clinical practice. Barrett’s Esophagus.  N Engl J Med. 2002;  346 836-842
• 7 Kumaravel A, Lopez R, Brainard J, Falk G W. Brush cytology vs. endoscopic biopsy for the surveillance of Barrett’s esophagus.  Endoscopy. 2010;  10 800-805
• 8 Geisinger K R, Teot L A, Richter J E. A comparative cytopathologic and histologic study of atypia, dysplasia, and adenocarcinoma in Barrett’s esophagus.  Cancer. 1992;  69 8-16
• 9 Robey S S, Hamilton S R, Gupta P K, Erozan Y S. Diagnostic value of cytopathology in Barrett esophagus and associated carcinoma.  Am J Clin Pathol. 1988;  89 493-498
• 10 Hardwick R H, Morgan R J, Warren B F. et al . Brush cytology in the diagnosis of neoplasia in Barrett’s esophagus.  Dis Esophagus. 1997;  10 233-237
• 11 Fritcher E G, Brankley S M, Kipp B R. et al . A comparison of conventional cytology, DNA ploidy analysis, and fluorescence in situ hybridization for the detection of dysplasia and adenocarcinoma in patients with Barrett’s esophagus.  Hum Pathol. 2008;  39 1128-1135
• 12 Falk G W. Cytology in Barrett’s esophagus.  Gastrointest Endosc Clin N Am. 2003;  13 335-348
• 13 Falk G W, Chittajallu R, Goldblum J R. et al . Surveillance of patients with Barrett’s esophagus for dysplasia and cancer with balloon cytology.  Gastroenterology. 1997;  112 1787-1797
• 14 Brankley S, Wang K K, Harwood A R. et al . The development of a flourescence in situ hybridisation assay for the detection of dysplasia and adenocarcinoma in Barrett’s esophagus.  J Mol Diagn. 2006;  8 260-267
• 15 Rygiel A, van Baal W, Milano F. et al . Efficient automated assessment of genetic abnormalities detected by flourescent in situ hybridization on brush cytology of a Barrett’s esophagus surveillance population.  Cancer. 2007;  109 1980-1988
• 16 Rygiel A, van Baal W, Milano F. et al . Assessment of chromosomal gains as compared to DNA content changes is more useful to detect dysplasia in Barrett’s esophagus brush cytology specimens.  Genes Chromosomes Cancer. 2008;  47 396-404
• 17 Kerkhof M, Kusters J, van Dekken H. et al . Biomarkers for risk stratification of neoplastic progression in Barrett esophagus.  Cell Oncol. 2007;  29 507-517