Sessile serrated adenoma/polyps with a minute T1 colorectal carcinoma

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An 80-year-old woman with no family history of cancer presented with abdominal pain and anemia. Colonoscopy revealed Campylobacter enterocolitis, and a 12 mm flat elevated lesion with VI pit pattern was incidentally detected in the ascending colon (Figure 1A). Magnifying narrow band imaging (NBI) revealed type IIIA capillary pattern (Figure 1B). Based on these endoscopic findings, submucosal invasive carcinoma was suspected. Endoscopic mucosal resection, by which the lesion was completely removed, was performed for histological evaluation. Histological examination revealed a serrated lesion with irregular branching crypts and/or L-shaped crypts as well as tumor invasion into the submucosa (Figures 2, arrow A, arrows: B). The patient was discharged after resolution of the colitis. At two years of follow-up, the patient has had neither recurrence of colitis nor evidence of metastasis. Serrated polyps belong to a heterogeneous group of lesions that are generally characterized morphologically. This type of lesion is thought to be a precursor of sporadic carcinomas with microsatellite instability, and is probably also a precursor of CpG islandmethylated microsatellite-stable carcinomas. We have previously reported that sessile serrated adenoma/polyps (SSA/P) show a significantly higher proliferative activity as compared to hyperplastic polyps, according to the diagnostic criteria for SSA/P established by the research project “Potential of Cancerization of Colorectal Serrated Lesions” by the Japanese Society for Cancer of the Colon and Rectum, which also indicate that SSA/P have crypt dilation, irregular branching crypts and horizontally arranged basal crypts (inverted T-and/or L-shaped crypts). Further, malignant transformation of SSA/P arises predominantly in the right side of the colon. Recently, in Japan as well as other countries, the incidence of advanced cancer in the right side of the colon has increased in elderly persons. The pathogenic and cancerization factors of SSA/P are of great clinicopathological importance.

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