**Abstract**

Subepithelial tumors (SETs) in the upper digestive tract are rare and only 10% of are located in the duodenum. Assessment of lesions protruding from the duodenal wall is difficult. Upper gastrointestinal (GI) endoscopy and computed tomography (CT) are not able to completely distinguish between different tumors and guide their subsequent management. Endoscopic ultrasonography (EUS) has a significant diagnostic yield in this context. EUS is able to accurately diagnose duodenal lesions, perform a biopsy if considered useful, guide the approach for resection and provide appropriate follow-up. SETs reported during upper GI endoscopy are more commonly cysts, polyps, lipomas, Brunner's gland adenoma, ectopic pancreas, gastrointestinal stromal tumors (GISTs) or neuroendocrine tumors (NETs). In addition, although more rarely, adenocarcinomas and lymphomas can be identified. EUS should be performed for any duodenal lesion larger than 1 cm that lacks the endoscopic characteristics of a cyst or a lipoma.

**Keywords:** subepithelial tumors, intramural lesions, endoscopic ultrasound, duodenum, endoscopy, interventional endoscopy

### **1. Introduction**

Lesions of the upper gastrointestinal (GI) tract are usually assessed by esophagogastroduodenoscopy (EGD), but less importance is shown for lesions of the small intestine. Protrusive lesions of the small intestine can arise from mucosa, with endoscopic features that allow their characterization. However, deep organ involvement cannot be assessed by endoscopy. The same is true for lesions from subepithelial layers, known as subepithelial lesions (SELs). These appear as bulging lesions covered by normal mucosa, and are firm as they are "palpated" with closed biopsy forceps. The mucosa covering these lesions is usually normal, and standard biopsies or "bite-to-bite" biopsies have low diagnostic accuracy. Assessing these lesions can be difficult, as computed tomography (CT) and magnetic resonance imaging (MRI) lack the resolution to properly describe them because of their size.

Endoscopic ultrasound (EUS) overcomes these drawbacks. Due to high resolution and ability to differentiate between all layers of the GI tract [1], EUS assesses the layer of origin, size, morphologic features, and involvement of the neighboring organs. Combined with the possibility of targeted biopsies from the deeper layers, EUS is the most effective for evaluating SETs of the duodenum.

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 from the muscularis usually need surgical intervention.


#### **Table 1.**

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

**75**

*Endoscopic Ultrasound Assessment of the Duodenal Wall Lesions*

**2. Evaluation of a duodenal subepithelial tumor**

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.

The endosonographic morphology of SETs is based on size, layer of origin, echogenicity, echotexture, vascularity and lymph nodes [2]. The procedure is difficult in cases of large lesions or inaccessible regions like the jejunum, ileum or,

Size should be reported in two orthogonal planes. There are five layers visible when examining the digestive tract. The first layer (hyperechoic) is the interface of the superficial mucosa with the contrast medium. The second layer (hypoechoic) is the deep part of the mucosa, containing the muscularis mucosae and lamina propria. The third layer (hyperechoic) is the submucosa and the interface between the submucosa and the muscularis propria. The fourth layer (hypoechoic) is the muscularis propria. The fifth layer is the serosa and the interface with adjacent structures. In addition, an SET described at EGD, as mentioned before, can actually be an extrinsic compression, originating beyond all layers. The relation with adjacent layers and structures has to be described. Are the layers immediately above and below distinguishable? Do they present ulcerations or irregularities? Can the neighboring structures be clearly distinguished or is there invasion? All these questions should be answered in a correctly redacted EUS result. The echogenicity of the tumor has to be noted. It can be anechoic (compare to the water in the lumen), hypoechoic (compare to muscularis propria), hyperechoic (compare to submucosa). The texture can also give useful information, as inhomogeneous lesions can raise suspicions of malignancy, as can irregular margins. For further description one can also mention the adjacent vascularization, presence of regional lymph nodes, hepatic lesions or free liquid in the peritoneum. Of all the characteristics mentioned, the most important are layer of origin and echogenicity (**Table 2**).

EUS without histological examination has a high diagnostic yield in duodenal SETs. Xu et al. reported an efficiency of up to 93.3% in a group of 75 duodenal SETs that had a later histological diagnosis [4]. However, diagnostic efficiency seems to be size related, as Brugge et al. reported a correct diagnosis in 45% of gastric lesions less than 2 cm in size and proposed, naturally, EUS with fine-needle aspiration (EUS-FNA) as the gold

*DOI: http://dx.doi.org/10.5772/intechopen.95927*

**2.1 Initial evaluation**

**2.2 Endoscopic ultrasound**

sometimes, the fourth part of the duodenum.
