II. Topics in EUS
EUS in submucosal tumors

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Definition of submucosal tumors

The term submucosal tumor (SMT) is really a misnomer because lesions in this category do not necessarily arise or confine themselves to the submucosa. Any growth underneath the mucosa of the GI tract whose etiology cannot readily be determined by lumenal diagnostic endoscopy or barium radiography is called an SMT (Fig. 1).

. Endoscopic picture of a duodenal SMT showing smooth overlying normal mucosa.

Experienced endoscopists often make an educated guess about the etiology of an SMT on the basis of

Symptoms

The majority of SMTs do not cause symptoms and are discovered incidentally during endoscopic or radiologic examinations. They occur in equal frequency in men and women, generally after the fifth decade. The overlying mucosa usually appears smooth and normal at endoscopy. On occasion, large submucosal neoplasms may outgrow their blood supply, ulcerate through the mucosa, and present with GI bleeding. Firm SMTs may also present with obstructive symptoms, especially if they are located near the

EUS imaging of SMTs

Optimal EUS imaging of an SMT requires submersion of the tumor under water.1, 2, 3, 4, 5 Depending on the SMT location, the patient may need to be repositioned after the GI lumen has been filled with water. “Submucosal tumors” related to extrinsic organs are usually easy to delineate.1, 2, 6 They cause extrinsic compression of the normal 5 EUS layers. For SMTs that are intrinsic to the GI wall (Table 1), it is important to characterize the layer(s) of origin or involvement, the echogenicity of

Extrinsic compressions

An enlarged (or sometimes normal) left atrium, left hepatic lobe, spleen (Fig. 3), prostate, or uterus may commonly masquerade as an SMT of the esophagus, stomach, or rectum during endoscopy.

. Gastric EUS demonstrates liver on the left side of the image and spleen on the right. Compression on the stomach by the enlarged spleen gave the appearance of an SMT.

The EUS characterization of these organs is well described.1, 2, 6 Engorged or tortuous vessels in association with these organs, for

GI stromal tumors

The most common SMTs encountered during GI endoscopy are GI stromal tumors (GISTs). They comprise about 1% of all GI tumors.10, 11, 12 These tumors were originally referred to as leiomyomas, leiomyoblastomas, and leiomyosarcomas10, 11, 12, 13, 14 because they bore a histologic resemblance to smooth muscle cells, and this incorrect terminology continues to be commonly used. The cell of origin of these neoplasms is mesenchymal, possibly the interstitial cell of Cajal.15, 16, 17, 18, 19, 20

Lipomas

Lipomas are the second most common SMTs encountered during endoscopy. They are generally soft and have a yellowish hue. It is not clear that performance of EUS is necessary for lipomatous lesions that are characteristically obvious. However, EUS might be useful when the endoscopic appearance is not definitive.1, 2, 3, 4, 5 Lipomas are typically identified as hyperechoic neoplasms in the third layer (Fig. 5).

. Left side of EUS image shows a hyperechoic lipoma (outlined by cursor marks) in the

Varices

Occasionally, large gastric varices may be polypoid.1, 5 The vascular nature of these “submucosal tumors” may not be evident at EGD because of the thick overlying rugal folds. EUS imaging of gastric varices demonstrates characteristic anechoic serpiginous structures in the third hyperechoic layer. In addition, EUS can identify perigastric collaterals, periesophageal collaterals, and penetrating vessels in patients with portal hypertension.

Cysts

Cysts in the GI tract may be a result of embryologic development, i.e., duplication cysts, or they may be the result of a resolved inflammatory process. Cysts appear as anechoic, rounded or ovoid, compressible structures in the third EUS layer of the GI tract (Fig. 6).28, 29, 30

. As seen on this EUS image, cysts are characteristically anechoic, round or oval structures.

The wall of inflammatory cysts will always be a single hyperechoic layer. The walls of duplication cysts may be imaged as a 3-

Carcinoids

EUS may be useful for imaging carcinoid tumors of the rectum and the stomach. These neoplasms are generally homogeneous, well demarcated, and mildly hypoechoic (Fig. 2).2, 31, 32 They are usually present in the first, second, and third layer. The behavior of GI carcinoids can be predicted by tumor size. If a carcinoid is less than 2 cm in longest diameter on EUS, it is unlikely to be malignant. If it is confined to the third layer and no adenopathy is identified, then endoscopic mucosal

Pancreatic rest

Ectopic pancreatic tissue deposits can also be submucosal. Most often found in the gastric antrum, these rests may appear as hypoechoic or mixed echogenicity lesions in the second, third, or fourth layer.1, 2, 3 The presence of ductal structures within the tissue is a distinctive finding but is found only in a minority of pancreatic rests.

Granular cell tumor

Granular cell tumors are benign submucosal neoplasms that may be found in the esophagus. They are believed to be of neural origin. EUS shows a heterogeneous mass with smooth borders located in the third (submucosa) layer.1, 33, 34

Submucosal metastases

Although uncommon, cancers may metastasize to the submucosa of the GI tract. Lymphomas may also present as submucosal masses. These malignant deposits are generally imaged as hypoechoic heterogeneous masses. They may involve any or all of the sonographic layers.1, 2, 3, 5

EUS fine-needle aspiration of submucosal lesions

Multiple investigators have used EUS guidance to obtain diagnostic histologic material from SMTs (Fig. 7).35, 36, 37, 38

. Fine-needle aspiration of submucosal tumor being performed with a curvilinear array ultrasound endoscope demonstrates the hyperechoic needle in the center of the mass.

Unfortunately, this approach has had limited success. A large majority of SMTs are GISTs. These neoplasms are very firm and a large amount of force is required to penetrate the neoplasm with a narrow-gauge

Role of EUS in guiding therapy of SMTs

Surgical resection is the only treatment that is effective for symptomatic GISTs. Surgery should also be performed on incidental GISTs that are large or have several EUS features associated with malignancy.20, 21, 22, 23, 24 GISTs that appear benign at EUS can be safely observed. The frequency with which characteristically benign asymptomatic lesions should be reimaged has not been determined but is likely in the order of several years. It is difficult to decide what to recommend to patients

Summary

In summary, EUS imaging is essential for the evaluation of “submucosal tumors.” The majority of these SMTs are benign and can be left alone. EUS-guided fine-needle aspiration can be considered for lesions that are not characterized by imaging alone but is of limited value when the SMT is a GIST. Information obtained by EUS can help guide decisions about endoscopic or surgical intervention.

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    Reprint requests: Amitabh Chak, MD, University Hospitals of Cleveland, 11100 Euclid Ave., Cleveland, OH 44106-1736.

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