Endoscopy 2013; 45(S 02): E235-E236
DOI: 10.1055/s-0033-1344321
Cases and Techniques Library (CTL)
© Georg Thieme Verlag KG Stuttgart · New York

Large serrated polyp with KRAS mutation in inflammatory bowel disease: a “nondysplastic dysplasia-associated lesion or mass (DALM)”?

L. Setaffy
1  Institute of Pathology, Medical University, Graz, Austria
C. Högenauer
2  Department of Internal Medicine, Division of Gastroenterology and Hepatology, Medical University, Graz, Austria
M. Lemmerer
3  Department of Surgery, Krankenhaus der Barmherzigen Brüder, Academic Teaching Hospital, Graz, Austria
C. Langner
1  Institute of Pathology, Medical University, Graz, Austria
› Author Affiliations
Further Information

Publication History

Publication Date:
14 August 2013 (online)

Patients with longstanding inflammatory bowel disease (IBD) have an increased risk of colorectal cancer. A causal link between chronic inflammation and cancer is well recognized. Precursor lesions include flat dysplasia (intraepithelial neoplasia) and elevated dysplasia, also known as dysplasia-associated lesion or mass (DALM) [1].

A 52-year-old woman with 20-year history of ulcerative colitis underwent surveillance colonoscopy, which disclosed a large irregular polyp in the sigmoid colon ([Fig. 1]). Biopsies showed a nondysplastic polyp with marked crypt dilatation and serration ([Fig. 2 a, b]). This polyp was completely removed and a second lesion clearly showing dysplastic glands was discovered at the rectosigmoid junction, and was diagnosed as high grade DALM ([Fig. 2 c, d]). Molecular analysis of the serrated polyp revealed KRAS mutation in exon 13 ([Fig. 3]); tests for BRAF mutation and microsatellite instability were negative.

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Fig. 1 a Large irregular polyp in the sigmoid colon in a 52-year-old woman with 20-year history of ulcerative colitis. b Note the discrete surface irregularities analyzed by narrow band imaging.
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Fig. 2 a, b Nondysplastic serrated polyp with marked crypt dilatation within the sigmoid colon (hematoxylin and eosin, original × 100). c, d Conventional high grade dysplasia-associated lesion or mass (DALM) at the rectosigmoid junction (hematoxylin and eosin, original × 200).
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Fig. 3 Molecular analysis (pyrosequencing of the KRAS gene) of the serrated polyp showing a somatic missense mutation in codon 13: wildtype control (upper panel) and serrated polyp (lower panel).

In 2008, Srivastava et al. [2] reported a series of three patients with longstanding IBD who developed numerous “hyperplastic/serrated” colonic polyps similar to those described in the “hyperplastic/serrated” polyposis syndrome. Two patients had synchronous colorectal cancer. KRAS mutation was detected in five of the 11 polyps. These findings suggested the possibility of a serrated pathway of carcinogenesis in IBD. In the sporadic setting, sessile serrated adenomas/polyps (SSA/P) are known precursors of mainly right-sided microsatellite instable cancers. They may also be regarded as indicator lesions, as these polyps have been associated with increased risk of synchronous and/or metachronous cancer growth, particularly of the proximal colon [3] [4].

We believe our case to be the first description of a solitary serrated polyp with KRAS mutation, similar to the lesions occurring as polyposis in longstanding IBD described by Srivastava et al. [2]. These non-dysplastic lesions may indicate increased risk of synchronous and/or metachronous advanced neoplasia and may be the equivalent of conventional DALMs with respect to cancer prediction (“nondysplastic DALM”).