What precisions can be made on differences between Barrett's epithelium and intestinal metaplasia by immunocytochemistry?
The role of a novel marker
L.H. Griffel, I. Baron-Gabriel,
P.S. Amenta, K.M. Das (New Brunswick)
Adenocarcinoma of the distal esophagus has had the fastest rising incidence of all cancers in the United States in the 1990's [1, 2] making the accurate diagnosis of potential premalignant lesions in this area more important than ever. It is well known that Barrett's esophagus (BE) is the single largest risk factor for adenocarcinoma of the esophagus, although much controversy has arisen in recent years as to what constitutes Barrett's esophagus. Classically BE has been classified as specialized intestinal type, cardia type or fundal type [3-5], with only specialized intestinal type thought to give rise to adenocarcinoma . Recently many authorities have begun to only consider specialized intestinal BE as BE and dismiss the other two types [7, 8].
We have developed a murine monoclonal antibody (IgM subtype) termed mAbDAS-1 (formerly known as 7E12H12) that has been shown to react both sensitively and specifically with BE (> 95%, 100%) . This antibody also reacts with some, but not all cases of gastric IM . This antibody was developed using hybridoma technique with a purified colonic protein as the antigenic protein. The antibody specifically reacts with colon epithelium, but not with epithelium from small intestine, or the rest of the gastrointestinal tract including normal stomach and esophagus . These facts lead us to believe that mAbDAS-1 is reacting with "colonic type" intestinal metaplasia. In this study we have attempted to answer the question of whether Barrett's esophagus is underdiagnosed using this antibody and comparing our results with alcian blue high iron diamine staining which is currently the gold standard for detecting colonic type intestinal metaplasia.
Endoscopy log books from the Robert Wood Johnson University Hospital were reviewed for the period 1/1/1993 to 3/31/1995. All cases that had an endoscopic diagnosis of Barrett's esophagus or rule out Barrett's esophagus were included. Tissue blocks from all biopsies taken from the esophagus during these cases were obtained and hematoxylin and eosin stained sections were reviewed. All sections containing glandular epithelium were included. Five micron tissue sections were cut from these samples and all were stained with mAbDAS-1 using a standard, highly sensitive immunoperoxidase technique and with alcian blue high iron diamine at pH 2.5.
Of the 27 cases containing glandular epithelium, 12 were felt to be definite Barrett's epithelium by the endoscopist and 15 were questionable for Barrett's epithelium. Of the
12 "BE" cases only 8 were read as consistent with BE by two pathologists. Eleven of these, however were positive for mAbDAS-1 reactivity, and these same 11 were positive for alcian blue high iron diamine staining. The areas of staining, though were not the same in all cases. Of the 15 "r/o BE" cases, only two were felt to be consistent with BE by two pathologists. These 2 and 2 others were positive for mAbDAS-1 reactivity. Again, the same 4 cases were positive for alcian blue high iron diamine, but the areas of staining were not the same in all cases. Additionally, the mAbDAS-1 staining is a clear and crisp golden brown, while the alcian blue staining of non-goblet cells was often difficult to appreciate.
Barrett's esophagus has been an area of much interest and controversy in recent years. With the dramatically rising incidence of adenocarcinoma of the esophagus much interest has been focused upon better diagnosis of BE. The issue of short-segment Barrett's has received a lot of attention and recent work suggests that the cancer risk from short segment Barrett's may be quite similar to that of traditionally classified Barrett's esophagus. The other important issue is what exactly constitutes Barrett's esophagus. The traditional classification includes three types; specialized intestinal, cardia type, and fundal type. As most data indicate that there is only an increased cancer risk for specialized intestinal type, many have begun to only consider this type as true BE.
Our data indicate that the current practice of only considering a patient to have BE if specialized intestinal type epithelium is present may not be accurate. The mAbDAS-1 marker has been shown to be very sensitive and specific for BE. If there is mAbDAS-1 reactivity in biopsy samples taken from the distal esophagus, it can quite accurately be considered BE. These results are corroborated by alcian blue high iron diamine staining, which is currently the gold standard for the diagnosis of BE, so even this method suggests that we are underdiagnosing BE. Given these facts, the current practice of only considering specialized intestinal epithelium in the esophagus BE is likely leading to the underdiagnosis of BE. While epidemiological data may indiciate that there is only an increased cancer risk in patients with specialized intestinal type BE, what we do not know is the progression of events that lead to the development of this type of epithelium. It is quite possible that cardia and fundus type BE do exist; as demonstrated by reactivity with the mAb, and given time it is possible that they may progress to the development of specialized intestinal type epithelium. Much further work is needed to demonstrate this with any degree of certainty, but by currently dismissing these patients as not having BE and therefore not undergoing any follow-up, they may be at an increased risk for the development of carcinoma.
Using standard diagnostic technique, namely H&E histology, up to 50 % of cases of BE may be under diagnosed as indicated by our data; 15 cases were detected by mAbDAS-1 staining and confirmed by alcian blue high iron diamine staining as opposed to 10 cases detected by H&E. This may, in part, explain the rising incidence of esophageal adenocarcinoma. If BE is not detected, these patients will not be screened and will be at higher risk of developing adenocarcinoma.
Our data indicate that the monoclonal antibody mAbDAS-1 may be an easy to use biomarker for the presence of Barrett's esophagus. Further research with this novel antibody may lead to the development of an easy to use screening test for the presence of colonic type change in the esophagus and may lead, in the long run, to a decrease in the incidence of adenocarcinoma of the esophagus through earlier detection of at risk patients.
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