Familial adenomatous polyposis (FAP) is an inherited cancer predisposition syndrome associated with numerous gastrointestinal tract adenomatous polyps, as well as gastric fundic gland polyps and pyloric gland adenomas in the upper gastrointestinal tract. While colonic FAP-associated traditional serrated adenomas (TSAs) have been reported in a few studies, small bowel FAP-associated adenomas with TSA morphology have not been characterized. This study describes the clinicopathologic and molecular findings of this type of adenoma in the small bowel of patients with FAP. We reviewed small bowel adenomas in 45 consecutive FAP patients to identify adenomas with zones showing slit-like serrations, cells with eosinophilic cytoplasm, ectopic crypt formation, and vesicular nuclei. Sporadic small bowel adenomas from 51 consecutive patients were also reviewed for adenomas with the same features. Of the 177 polyps from 45 FAP patients and 60 polyps from 51 nonsyndromic patients, 18 TSAs from 9 FAP patients (20%) and 10 TSAs from the sporadic group (19.6%) were identified. FAP patients presented at a younger age than nonsyndromic patients (median: 43 vs. 66; P=0.0048). FAP-associated TSAs were asymptomatic and smaller than sporadic TSAs (median size: 0.6 vs. 2.5 cm; P=0.00006). Immunostaining for β-catenin and testing for BRAF and KRAS mutations were performed in a subset of the cohort. Nuclear β-catenin was seen in 1 FAP-associated TSA and 3 nonsyndromic TSAs. All TSAs (FAP-associated and nonsyndromic) showed wild-type BRAF, while KRAS mutations were identified only in the nonsyndromic setting. In summary, small bowel FAP-associated and sporadic TSAs share a similar morphology, and the BRAF-serrated pathway does not contribute to their pathogenesis.

中文翻译：

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家族性腺瘤性息肉病相关的传统小肠锯齿状腺瘤：临床病理学和分子分析。

家族性腺瘤性息肉病（FAP）是一种遗传性癌症易感综合征，与大量胃肠道腺瘤性息肉以及上消化道胃底腺息肉和幽门腺腺瘤相关。虽然一些研究报道了结肠 FAP 相关的传统锯齿状腺瘤 (TSA)，但具有 TSA 形态的小肠 FAP 相关腺瘤尚未得到表征。本研究描述了 FAP 患者小肠中此类腺瘤的临床病理学和分子学发现。我们对 45 名连续 FAP 患者的小肠腺瘤进行了检查，以识别具有狭缝状锯齿状区域、具有嗜酸性细胞质的细胞、异位隐窝形成和泡状核的腺瘤。还对 51 名连续患者的散发性小肠腺瘤进行了检查，以确定是否存在具有相同特征的腺瘤。在 45 名 FAP 患者的 177 颗息肉和 51 名非综合征患者的 60 颗息肉中，鉴定出 9 名 FAP 患者的 18 颗 TSA（20%）和散发组的 10 颗 TSA（19.6%）。FAP 患者的发病年龄比非综合征患者更年轻（中位数：43 比 66；P=0.0048）。FAP 相关 TSA 无症状且小于散发性 TSA（中位大小：0.6 与 2.5 厘米；P=0.00006）。在队列的一个子集中进行了 β-连环蛋白免疫染色以及 BRAF 和 KRAS 突变测试。在 1 个 FAP 相关 TSA 和 3 个非综合征 TSA 中发现核 β-连环蛋白。所有 TSA（FAP 相关和非综合征）均显示野生型 BRAF，而 KRAS 突变仅在非综合征环境中被发现。总之，小肠 FAP 相关性和散发性 TSA 具有相似的形态，并且 BRAF 锯齿状通路对其发病机制没有贡献。