Diagnostic value of endoscopic and endoscopic ultrasound characteristics of duodenal submucosal tumour-like heterotopic gastric mucosa

1Department of Gastroenterology and Medicine; 2Department of Pathology, Fukuoka University School of Medicine, Fukuoka, Japan Correspondence and reprints: Dr Koichi Eguchi, Department of Gastroenterology and Medicine, Fukuoka University School of Medicine, 7-45-1, Nanakuma, jounan-ku, Fukuoka city, Japan. Telephone 81-92801-1011, fax 81-92-874-2663, e-mail keguchi@minf.med.fukuoka-u.ac.jp Received for publication May 19, 2010. Accepted November 22, 2010 The presence of heterotopic gastric mucosa (HGM) is well known in all organs of the gastrointestinal tract, particularly in the esophagus, duodenum and ileum (Meckel’s diverticulum) (1-4). A recent study (5) observed duodenal HGM in 8.9% of 28,210 patients who underwent esophagogastroduodenoscopy (EGD), and is endoscopically recognized as solitary or multiple small nodules (4,6,7). Morphologically, submucosal tumour-like masses are frequently of the solitary type (2,7-9). Solitary large HGMs may be difficult to differentiate from malignant neoplasms such as carcinoma, carcinoid tumours or lymphoma (1); however, a differential diagnosis for it has yet to be established. Herein, we describe the endoscopic and endoscopic ultrasound (EUS) features of six cases of duodenal HGM with submucosal tumour-like appearance in the bulb and descending duodenum.


ResULts
The clinical, endoscopic and EUS results are summarized in Table 1.The affected sites were the descending duodenum in four patients and the bulb in two.Endoscopically, the lesions appeared as solitary, sessile, submucosal tumour-like masses with a wide base and a depression at the top of the lesion (Figures 1A, 1B and 1C).The remaining surface of the masses was covered mainly with normal duodenal mucosa.In four of six lesions analyzed, small granular structures were found in the depressed area (Figure 1D).
On EUS, the tumours were demonstrated to be heterogeneously hypoechoic masses with small anechoic areas (Figures 2A and 2B).The tumours ranged from 6 mm to 16 mm in diameter, and were localized within the second to third layers, which appeared to correspond to the mucosa and submucosa, respectively.
Histologically, all lesions consisted of gastric glands with or without some dilated glands, which were visualized as small anechoic areas on EUS (Figures 2A and 2B) and covered with normal duodenal epithelium without metaplastic change (Figure 3A).In four cases, tumours were composed of gastric-type foveolar epithelium showing papillary growth involving the fundic glands and pyloric glands (Figure 3B).The others consisted of gastric-type foveolar epithelium and pyloric glands.No atypical cells were observed in any cases.No tumour recurrence developed in the three patients who underwent polypectomy.

dIsCUssIoN
Jepsen et al (10) reported that duodenal polyps were found in 4.6% of patients referred for upper endoscopy, and that 1.4% of these duodenal polyps were HGM.A more recent study (5) reported a prevalence of duodenal HGM of 8.9% in patients undergoing EGD.
Histologically, previous reports (4,6,7) described HGM as comprised of solitary or multiple nodules.The proportion of the latter exceed 70%, whereas that of solitary lesions was small and ranged from 0% to 30%.Uraoka et al (7) described solitary lesions as hemispherically shaped and approximately 10 mm in diameter.Conversely, multiple-type lesions were demonstrated to be small nodules of various sizes.Each nodule exhibited an ovoid shape and plate-like elevation, with a diameter of 2 mm to 5 mm.In the present report, we described six cases of hemispherical HGM with a submucosal tumour-like appearance.Similar endoscopic findings of HGM have been reported by other investigators (2,7-9).Possible differential diagnoses include Brunner's gland  hyperplasia, ectopic pancreatic tissue, benign lymphoid hyperplasia, lymphoma, leiomyoma, leiomyosarcoma, adenoma, carcinoma and carcinoid tumours (1,8).
In the present series, a unique endoscopic finding was identified in 66% of patients, specifically small granular or lobular structures within the depressed portion of the lesion.Some investigators reported that large solitary duodenal HGMs tended to exhibit central depression (7,9,11).However, these features can also be seen in Brunner's gland hyperplasia, carcinoid tumour, metastatic neoplasm or malignant lymphoma (1,8,9).Thus, it may be difficult to distinguish duodenal HGMs from other submucosal tumours using endoscopy.
EUS provides valuable information for the diagnosis of submucosal tumours of the gastrointestinal tract (12) because it is able to safely and precisely visualize size, extent, the layer of origin of the lesions and obtain internal images precisely (13).However, specific EUS features of duodenal HGMs are scarce.Hizawa et al (14) described that duodenal HGMs reveal simple anechoic masses within the submucosal layer on EUS.The EUS findings in our cases included hypoechoic and several small anechoic areas predominantly within the submucosal layer.We believe that the internal echo pattern of HGMs is variable and in accordance with the size of dilated gastric-type glands, which is characteristic of HGM.
An alternative approach for the differential diagnosis of HGM is Tc-99m pertechnetate scintigraphy.Tc-99m pertechnetate abdominal scintigraphy is a useful method for diagnosing and locating ectopic gastric mucosa in Meckel's diverticulum, enteric or gastric duplications and cysts, Barrett's esophagus and islands of HGM in an otherwise normal bowel.The method has an overall accuracy of 90% and a sensitivity of 85% in surgically proven cases (15).
Excessive surgery should be avoided because HGM is essentially a benign entity.However, if the HGM is large, it may still require laparoscopic or endoscopic resection due to the risk of ulceration, bleeding, adenoma or adenocarcinoma in the HGM, as previously reported (8,9,(16)(17)(18).Endoscopic resection may be applied in the case of duodenal HGMs when EUS can verify that the tumour is localized in the third layer, which corresponds to the submucosa of the duodenal wall.EUS demonstrated that three lesions (patients 1, 2 and 3) were localized in the mucosa and submucosa.We carefully performed endoscopic polypectomy with electrocautery snare for removal, and obtained precise histological diagnosis of the tumours.These three patients developed no complications from the resection.

CoNCLUsIoN
We showed that heterogeneously hypoechoic masses with several small anechoic lesions on EUS, and small granular structures on the depressed portions of the lesion, may be a characteristic feature of HGMs.Finally, EUS may not only provide characteristic findings, but also indicate the appropriateness of endoscopic resection.

Figure 1 )
Figure 1) A and B: Patient 1 and 6.Endoscopy showing a wide-based sessile submucosal tumour-like mass with depression at the top of the lesion.The lesions are covered mainly by normal duodenal mucosa.C Patient 3. Endoscopy showing a wide-based sessile submucosal tumour-like mass without granular structures at the top of the lesion.d Patient 4. Small granular structures are found in the depressed area

Figure 2 )
Figure 2) A Patient 1. Endoscopic ultrasound images showing a heterogeneously hyperechoic mass with several anechoic lesions located predominantly in the submucosa.B Patient 3. Endoscopic ultrasound image showing a heterogeneously hyperechoic mass with anechoic lesions located predominantly in the submucosa