Diagnosis and grading of dysplasia in Barrett's oesophagus.

This review focuses on the pathological features of dysplasia in Barrett's oesophagus. Two categorisation schemes are used for grading dysplasia in the gastrointestinal tract, including Barrett's oesophagus. The inflammatory bowel disease dysplasia morphology study group system is the one most commonly used in the USA. However, some European and most far Eastern countries use the Vienna classification system, which uses the term "non-invasive neoplasia" instead of low-grade dysplasia (LGD) or high-grade dysplasia (HGD) and also uses the term "suspicious for invasive carcinoma" for lesions that show equivocal cytological or architectural features of tissue invasion. The degree of dysplasia is based on a combination of cytological and architectural atypia. However, the precise number of HGD crypts that is necessary to upgrade a biopsy from LGD to HGD has never been investigated and varies widely among expert gastrointestinal pathologists. The extent of dysplasia, particularly LGD, has also been recognised recently as an important prognostic parameter in Barrett's oesophagus. Other problematic areas of dysplasia interpretation include differentiation of regenerating epithelium versus LGD and separating HGD from carcinoma. Dysplasia associated with macroscopically visible lesions, such as ulcers, nodules or polyps, carry a high risk of synchronous or metachronous adenocarcinoma. Recently, immunostaining for alpha-methylacyl-CoA-racemase has been shown to have a high degree of specificity for detection of dysplasia in Barrett's oesophagus and may be used to help distinguish negative from positive biopsies in this condition. In this review, the problematic areas in dysplasia interpretation are outlined and a specific approach to these issues is discussed.