**2.1 Initial evaluation**

*Endoscopy in Small Bowel Diseases*

SETs of the duodenum can be true intramural lesions of the duodenal wall or extrinsic compressions. Extrinsic compression comes from adjacent structures, like the gallbladder or blood vessels. Around 1 in 5 SETs found in the upper GI tract is an extramural compression [2, 3]. Data regarding external compressions on the duodenum are few, but clinical experience suggests that they are less frequent than in the stomach. Intramural lesions can be true submucosal or pseudo-submucosal lesions. The latter are usually polyps or inflammatory lesions. True submucosal lesions originate from one of the deeper layers of the duodenal wall. Benign SETs of the duodenum include cysts, gastrointestinal stromal tumors (GISTs), leiomyomas (very rare) of the minor papilla (which at EGD can be confused with SETs), lipomas, neuroendocrine tumors (NETs) and ectopic pancreas. Malignant SETs can be malignant mesenchymal tumors, adenocarcinomas or lymphomas (**Table 1**). A correct and complete diagnosis of an SET, including extension and proximity to other structures, is essential in deciding the following steps, as the complex localization and surroundings of the duodenum make surgical interventions difficult. Its thin walls and proximity to the biliary and pancreatic ducts makes even endoscopic therapeutic interventions more prone to serious complications like perforation. In this context, the diagnosis, prognosis and possible therapeutic options should always be properly weighed and presented to the patient before a decision is made. SETs should be resected, endoscopically or surgically, if there is a suspicion of malignancy or if they are symptomatic. Tumors with malignant potential, like GISTs or NETs, should be resected, or in certain circumstances followed endoscopically. EUS can help guide the treatment. Generally, lesions limited to the mucosa and submucosa can be removed endoscopically, with a high safety profile, using advanced techniques like endoscopic submucosal resection (ESD). Tumors arising

**Xu et al. [4] Markovic et al. [5] Kawamoto et al. [6]**

from the muscularis usually need surgical intervention.

**Mucosal lesions**

**Submucosal lesions**

Total number 169 80 24

Inflammatory protruding or polyps 36 (21%) 13 (16%) 1(4%)

Cysts 40 (24%) — 8(34%) Brunner's adenoma 25(15%) 7 (9%) 6(25%) Lymphangioma — — 1(4%) Lipoma 6 (4%) 6 (8%) 1(4%) Ectopic pancreas 19(11%) — 1(4%) Stromal tumors 17 (10%) 33 (41%) 1(4%) NET — 3 (4%) — Gangliocytic paraganglionas — — 1(4%)

Extrinsic compression 12(7%) — — Minor papilla 12(7%) — —

Malignant tumors 2 (1%) 18 (22%) 4(17%)

*Different studies evaluating the final diagnosis in duodenal lesions referred to EUS. Most, but not all, are* 

**74**

**Table 1.**

**Others**

**Malignant tumors**

*confirmed histologically after EUS.*

SETs identified in the upper GI tract are rare, being found in around 1 in 300 EGDs [7]. Only around 10% of those are located in the duodenum [8]. The true prevalence probably remains unknown, as most SETs are asymptomatic and are found to be completely unrelated to the reason the EGD was performed. In a study involving 346 EUS examinations of upper GI SETs, 87% of the lesions were unrelated to the presenting symptoms of the patient [2]. The rare symptomatic cases usually manifest through occult bleeding or abdominal pain. Evaluation of a duodenal SET starts during the initial EGD. Its location, size, mobility and color should be noted. Modifications of the mucosa and "tenting" sign are also important. A firm lesion with a "pillow" sign is usually a lipoma, while a firm and translucent lesion can be a cyst. A central depression along mucosal irregularities can suggest an ectopic pancreas, while a central ulceration can be a sign of a GIST. Mucosal biopsies are rarely useful, as they only touch the mucosa and are unable to retrieve tissue from the lesion. More invasive methods, like "buttonhole" biopsies or jumbo forceps, are not always successful and carry high risk of adverse events [9]. If the lesion is not a cyst or lipoma, tissue acquisition should be performed for diagnosis, especially because some of the duodenal SELs have malignant potential.
