Duodenal Foveolar Adenoma: Case Presentation with Whole Exome Sequencing and Review of the Literature.

<p>Introduction: Duodenal adenomas are most commonly associated with polyposis syndromes. Foveolar adenoma is an especially rare entity with an unknown aetiology. We present a case of duodenal foveolar adenoma with coexisting metaplasia, whole exome sequencing results, and the first literature review. Case Presentation: Hereby, we present the case of a 58-year-old man, whose polypectomy specimen revealed a lesion composed of mainly foveolar cells with low-grade dysplasia and was concluded as foveolar adenoma. Due to the incomplete resection, polypectomy was repeated; this time, foveolar adenoma was diagnosed with high-grade dysplasia. Foveolar differentiation was proved with MUC5AC immunohistochemistry; in addition, KRAS and SMAD4 pathogenic mutations were identified. Discussion: Duodenal foveolar adenoma remains a controversial and an enigmatic entity. Our paper presents such a lesion with first low-grade, then high-grade dysplasia, and KRAS mutation, identical to gastric manifestations. The further sample of our patient suggests foveolar metaplasia as an aetiological factor that supports the literature data. </p>.