Adenoma without Dysplasia: What Does It Mean?

We read with great interest and surprise the article by Kiesslich et al. [1] on the results of chromoendoscopy with indigo carmine in improving the detection of adenomatous and nonadenomatous lesions in the colon. The authors describe a method of detecting very small lesions using vital staining with indigo carmine dye, which reveals multiple mucosal lesions that are not identified on routine video endoscopy. They used the classification by Kudo et al. [2] for pit patterns seen after staining with the above method, and validated its usefulness for differentiating between hyperplastic and adenomatous lesions.

During the authors' first, routine colonoscopic examination, 105 visible lesions were found, in 54 of which adenomas were diagnosed histologically. However, only 23 of the 54 adenomas (42.6 %) represented low-grade or high-grade intraepithelial neoplastic lesions, equivalent to the presence of dysplasia. The remaining 31 adenomas (57.4 %) are described as “adenomas without dysplasia” (see Table 2 of the paper).

Subsequently, 178 additional lesions were then found after indigo carmine spraying. According to the authors, there were 165 hyperplastic polyps, 10 adenomas not otherwise specified, and three adenomas with intraepithelial neoplasia (one high-grade and two low-grade). Thus, 41 out of a total of 67 adenomas (61.2 %) were diagnosed as such without showing features of intraepithelial neoplasia (dysplasia).

Categorizing lesions in this way may mislead an unwary reader. Similar doubts are expressed by Lambert and Rey [3], the authors of the editorial accompanying the report by Kiesslich et al. [1]. They question whether “so-called adenoma without dysplasia” may correspond to the group termed “indefinite for dysplasia” in the Vienna classification [4]. In our opinion, this is not the case, since in the Vienna classification adenomas only belong to the third and fourth categories of “noninvasive low- and high-grade neoplasia”. The second category in the Vienna classification, termed “indefinite for neoplasia/dysplasia” does not relate to adenomas. Similar recommendations for adenoma terminology are given by Lewin [5]. The group of lesions described as “indefinite for dysplasia” in the Vienna classification does not meet the criteria necessary for a diagnosis of dysplasia, and is especially reserved for cases in which a pathologist is unable to decide whether a lesion presents neoplastic or nonneoplastic features. In such cases, doubts may be resolved by repeated, more adequate biopsies, or after removing possible sources of cellular hyperproliferation or atypia, such as inflammation.

The question therefore arises of what the term “adenoma without dysplasia” means, and whether one can diagnose an adenoma without cellular dysplasia. It is of the utmost importance to distinguish large-intestinal polyps with malignant potential from those that have no relationship to cancer. Ever since the early classifications of colorectal polyps, adenomas have always been described as a separate group of neoplastic lesions, since all of them share two basic features of neoplasia - i. e., dysregulated proliferation and failure to differentiate fully [6] - which are reflected in the cytological changes known as “epithelial atypia”, or “dysplasia” of their epithelium [7] [8] [9] [10]. From the early 1970s, great emphasis has been placed on the pathology of the adenoma - carcinoma sequence [9] [10].

In our opinion, the endoscopic descriptions and figures presented by Kiesslich et al. [1] are typical for those of aberrant crypt foci (ACF), which are divided into two histological types - hyperplastic and dysplastic (microadenomas) - in the World Health Organization classification [11]. Pit patterns on the mucosal surface, evaluated by means of magnifying endoscopy, allow reliable prediction of the histology. In a large series of ACFs reported by Nascimbeni et al., the authors describe mixed hyperplastic and adenomatous crypts [12]. They also suggest that carcinogenesis in the large intestine involves a progression from ACF through adenoma to carcinoma. It is odd that none of these mixed hyperplastic and adenomatous crypts are described in the report by Kiesslich et al. [1]. In addition, 93 % of the adenomas in the report - either with or without intraepithelial neoplasia - are classified as having pit patterns III - V (Table 2). If so, the pit pattern would be of no value in predicting the histology and potential for malignant transformation. We are therefore unable to agree with the authors' statement regarding a 92 % sensitivity and 93 % specificity using pit patterns I - II and III - V to distinguish between nonneoplastic and neoplastic lesions.

References

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