Serrated adenomas with a BRAF mutation in a young patient with familial adenomatous polyposis

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Serrated adenomas with a BRAF mutation in a young patient with familial adenomatous polyposis Kentaro Moriichi 1 & Hiroki Tanabe 1 & Yusuke Ono 2 & Yu Kobayashi 1 & Yuki Murakami 1 & Takuya Iwama 1 & Takehito Kunogi 1 & Takahiro Sasaki 1 & Keitaro Takahashi 1 & Katsuyoshi Ando 1 & Nobuhiro Ueno 1 & Shin Kashima 1 & Hidehiro Takei 3 & Yusuke Mizukami 1,2 & Mikihiro Fujiya 1 & Toshikatsu Okumura 1 Accepted: 25 May 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020

Abstract Introduction Familial adenomatous polyposis (FAP) is typically characterized by more than hundred adenomatous polyps in the colorectum, caused by germline APC mutation. A small proportion of the polyps progress to colorectal adenocarcinoma via adenoma-carcinoma sequence. Serrated lesions and polyps, characterized by a serrated architecture of the epithelium, are noted for two types of genetic pathways in colorectal carcinogenesis. BRAF and KRAS mutations are observed in the serrated pathway. Case Report We report a young FAP patient with rectal serrated adenomas that were removed by colonoscopic procedures. The histological features with villiform projections and slit-like serration indicated traditional serrated adenoma. A genetic examination with next-generation sequencing showed a somatic BRAF mutation in the serrated adenoma and APC mutations in the tubular adenomas. His germline mutation was found at APC p.Q1928fs*. Conclusion Serrated adenomas with dual genetic alterations in a FAP patient may be associated with colorectal carcinogenesis and should be considered a target lesion for treatment. The present study demonstrated the malignant potential of serrated adenoma in a FAP patient. Keywords TSA . Colorectal cancer . Next-generation sequencing . Genetic tumor syndrome

Introduction Colorectal cancer is one of the most common types of malignancy, and its incidence is increasing worldwide. Surveillance colonoscopies, for the diagnosis and prevention, are recommended in the recent UK guidelines for the management of hereditary colorectal cancer [1].

* Hiroki Tanabe [email protected] 1

Division of Gastroenterology and Hematology/Oncology Department of Medicine, Asahikawa Medical University, Midorigaoka-Higashi 2-1-1-1, Asahikawa, Hokkaido 078-8510, Japan

2

Institute of Biomedical Research, Sapporo-Higashi Tokushukai Hospital, Sapporo, Hokkaido, Japan

3

Department of Diagnostic Pathology, Asahikawa Medical University Hospital, Asahikawa Medical University, Asahikawa, Hokkaido, Japan

Most colorectal cancers develop via the conventional pathway through the classic adenoma-carcinoma sequence in pathogenesis. The most frequent genetic changes in the conventional pathway are alterations in APC, KRAS, TP53, SMAD4, and PIK3CA [2]. Somatic alterations in APC are found in about 80% of colorectal adenomas and carcinomas and are known to occur very early in the pathway. The most recent World Health Organization (WHO) classification of digestive system tumors published in 2019 comprehensively described colonic precu