MALIGNANT TRANSFORMATION OF SESSILE SERRATED ADENOMAS – NBI DIAGNOSIS AND ESD OF TWO CASES

Sessile serrated adenomas (SSA) are potentially responsible for the apparition of interval colorectal cancer (CRC) [1]. Their malignant transformation does not follow the classical molecular pattern [2].

SSA are more difficult to detect in endoscopy. The endoscopic diagnosis is based on white light imaging (WLI) and narrow band imaging (NBI) with magnification, using the WASP criteria [3].

We report here 2 atypical nongranular LSTs that had both sessile serrated criteria (WASP) but also a classical adenoma/adenocarcinoma component. ESD was performed using the clip-traction strategy [4].

First patient had a 3 cm non-granular lateral spreading tumour (LST) in the left colon, Paris IIB, with Kudo Vi pit pattern but also crypts with dark spots (Figure 1,2). En bloc ESD was performed. We closed the large mucosal defect with clips and a rubber band [5]. Histology revealed complete resection of a degenerated SSA with in-situ carcinoma.

The second patient had a cm non-granular LST was found on the sigmoid, Paris 0-IIa + 0-IIc, Kudo Vn with nearly avascular capillaries (Sano IIIB) (Figure 3). ESD was performed because of comorbidities and high surgical risk. Histology revealed complete resection of a SSA with a focal moderately differentiated adenocarcinoma that was deeply invading (2200 µm) the submucosa, tumoral budding but no vascular or lymphatic invasion. Complementary surgical intervention was recommended.

Both this lesions had 2 distinct components: a classical adenomatous and also a sessile serrated one with dark spots inside crypts, a clouded surface and irregular shape. There were no complications after ESD.

Malignant transformation has rarely been described within a SSA but appears as a conventional adenomatous malignancy. In those transformed lesions, two components are clearly identified. Endoscopic evaluation using NBI with dual focus magnification is very important, in order to decide for the best resection strategy based on the worst component after histology prediction.