Two duodenal sessile serrated lesions in a patient with serrated polyposis syndrome: case report and review of the literature.

The serrated neoplastic pathway has been reported to be involved in the development of colorectal cancer, and serrated lesions are recognized to have malignant potential. Recently, serrated lesions of the duodenum have been increasingly reported. Serrated polyposis syndrome (SPS) is characterized by multiple serrated lesions in the colon; however, it is unknown whether serrated lesions in the duodenum occur in patients with SPS. A 58-year-old man with SPS underwent a routine colonoscopy. When he underwent esophagogastroduodenoscopy for screening, two 4-mm white flat-elevated lesions in the second portion of the duodenum were found. The biopsy results were suggestive of sessile serrated lesions (SSLs); therefore, we performed endoscopic mucosal resection with a cap-fitted pan-endoscope for therapeutic purposes. Pathology results showed an SSL in the duodenum. One SSL lesion was positive for the BRAF mutation; multiple duodenal SSLs in patients with SPS are rare, and there are no previous reports of BRAF mutation-positive SSLs. The grade and molecular abnormalities of duodenal SSLs are currently unknown, as is the relationship between SPS and duodenal SSL. Further case accumulation is expected.