Tumours in the Small Bowel **

Small bowel tumours are rare and originate from a wide variety of benign and malignant entities. Adenocarcinomas are the most frequent primary malignant small bowel tumours. Submucosal tumours like gastrointestinal stromal tumours (GIST) or neuroendocrine tumours (NET) may show a central umbilication, pathologic vessels, bridging folds or an ulceration of the overlying mucosa. These signs help to differentiate them from harmless bulges caused by impression from outside, e.g. from other intestinal loops. Sarcomas of the small bowel are rare neoplasias with mesenchymal origin, sometimes presenting as protruding masses. Benign tumours like lipoma, fibrolipoma, fibroma, myoma, and heterotopias typically present as submucosal masses. They cannot be differentiated endoscopically from those with malignant potential as GIST or NET. Neuroendocrine carcinomas may present with diffuse infiltration, which may resemble other malignant tumours. The endoscopic appearance of small bowel lymphomas has a great variation from mass lesions to diffuse infiltrative changes. Melanoma metastases are the most frequent metastases to the small bowel. They may be hard to distinguish from other tumours when originating from an amelanotic melanoma.