British Journal of Radiology 75 (2002),624-626 © 2002 The British Institute of Radiology
Gastric schwannoma: MRI findings
N Karabulut, MD
D R Martin, MD, PhD
and
M Yang, MD
Department of Radiology, West Virginia University Hospitals, Morgantown, WV, USA
Correspondence: N Karabulut, MD, Hastane Cad. Umut Apt 5/3, 20010, Denizli, Turkey
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Abstract
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MRI features are described in a case of gastric schwannoma. A large, discretely marginated, multilobular mass was seen adjacent to the gastric antrum with the epicentre of the mass in the gastrocolic ligament. The overall signal pattern was low on T1 weighted images and moderate to markedly elevated on T2 weighted images. Post-gadolinium sequences demonstrate slow but fairly uniform enhancement throughout the mass.
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Introduction
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Schwannomas are rare among the spindle cell mesenchymal tumours of the digestive tract, arising from the Schwann cells of the neural plexus of the gastrointestinal wall. Gastric schwannomas, most commonly sited in the stomach, account for only 0.2% of all gastric tumours [1] and have received little attention in radiological literature. These tumours are usually asymptomatic or may present as upper gastrointestinal bleeding or as mass lesions [1–7]. Upper endoscopy is important in the initial evaluation of these patients, but it may not be helpful in the diagnosis of submucosal tumours growing exophytically. Cross-sectional imaging findings may be useful in the detection and characterization of the tumour and its relation with surrounding organs. We describe here the MRI features of gastric schwannoma in a 46-year-old patient. To our knowledge, this case is the first to be reported with MRI documentation.
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Case report
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A 46-year-old White male was seen in surgery clinic with the complaint of inguinal hernia. On physical examination the patient was found to have a large abdominal mass in his right upper quadrant. The patient denied any complaints or any symptoms related to the mass. Laboratory findings were within normal limits. Upper endoscopy showed large extrinsic bulges from both the anterior and posterior walls in the gastric antrum. Multiple biopsies taken from the site of extrinsic mass revealed marked chronic active gastritis without evidence of a malignancy. The patient subsequently underwent abdominal MRI in order to evaluate the mass, which showed a large, discretely marginated mass with innumerable lobulations centered in the region of the gastrocolic ligament (Figure 1
). The overall signal pattern was low on T1 weighted images and moderate to markedly elevated on T2 weighted images (Figure 1a, b). Each of these lobulations appeared to be encapsulated with moderately well defined borders, which were seen as markedly hypointense on T1 weighted images and hypointense, isointense and hyperintense on T2 weighted images. Post-gadolinium sequences demonstrate slow but fairly uniform marked enhancement throughout the internal aspect of each of the lobules (Figure 1c, d). However, the hypointense borders around the lobulations remained unenhanced. There was no evidence of necrosis within the tumour mass. The inferior aspect of the mass was pushing on the transverse colon with the transverse colon draped around the mass. The superior aspect of the mass was seen extending over the anterior aspect of the gastric antrum, pylorus, duodenal cap and proximal part of the second segment of the duodenum towards the gall bladder fossa and porta hepatis. The distal stomach appeared to be squeezed by the mass (Figure 1a, b, d). The pancreas was pushed posteriorly and inferiorly but was clearly separate from the mass. The remainder of the abdomen was unremarkable without evidence of direct organ invasion, lymphadenopathy or solid organ metastases. The celiac artery and major branches, as well as the superior mesenteric artery and major branches, were clearly identified but a vascular supply to the mass was not well demonstrated.
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Figure 1. 46-year-old man with gastric schwannoma. (a) Axial fat-suppressed T1 weighted fast spoiled gradient echo MR image (FLASH: TR/TE, 258/5.9 msec) at the level of the gall bladder shows a hypointense mass in the region of gastrocolic and gastrohepatic ligaments squeezing the gastric antrum (arrows). (b) Coronal T2 weighted fast steady state MR image (True FISP: TR/TE 4.6/2.3 msec) through the stomach shows a multilobulated mass centred in the gastrocolic ligament exhibiting areas of moderate to markedly elevated signal. Note the close relation of the mass to gastric antrum. (c) Axial fat-suppressed T1 weighted fast spoiled gradient echo MR image (FLASH: TR/TE, 168/5.9 msec) after iv administration of gadolinium demonstrates fairly uniform intense enhancement throughout the internal aspect of each of the lobules. The hypointense borders surrounding the lobules remain unenhanced. (d) Axial fat-suppressed T1 weighted volumetric three-dimensional gradient echo MR image (TR/TE, 3.7/1.7 msec) at the level of the gastric antrum after iv administration of gadolinium delineates the relationship between the mass and the stomach to a better degree.
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At exploratory laparatomy, the abdominal mass was found to be adhered to the greater curvature in the anterior wall of the distal stomach. Since the mass was arising from the distal portion of the stomach, a partial gastrectomy with Billroth I gastroduodenostomy was performed in order to remove the mass. Macroscopic examination revealed a yellow–tan bosselated tumour, which measured 15 cm xtimes;times; 12 cm xtimes;times; 11 cm in size. The cut surface of this tumour was yellow–tan and focally haemorrhagic with a fish flesh appearance. Sections from the gastric tumour showed a spindle cell neoplasm arranged in a palisading fashion with numerous Verocay bodies. In addition, more cellular Antoni type A patterns were seen alternating with looser Antoni type B areas. Mitoses were not seen and cytologic atypia was not appreciated. The tumour cells were strongly positive for S100 and vimentin, and negative for smooth muscle actin, keratin and CD34. The histological and immunohistochemical features were consistent with a benign Schwannoma.
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Discussion
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Schwannomas, also known as neurinoma and neurilemmoma, are benign, slow growing neoplasms originating in any nerve that has a Schwann cell sheath. They rarely occur in the digestive tract, but when they do the most common site is the stomach, and represent 0.2% of all gastric tumours [1]. Gastric schwannomas occur more frequently in the third to fifth decade of life and are usually solitary tumours arising from the fundus, body or antrum of the stomach [1–7]. However, they can occur in children and, rarely, can be malignant [8]. Commonly they are intramural, although they can be extraluminal or endoluminal [2]. Gastric schwannomas are usually covered by intact mucosa and principally involve the submucosa and muscularis propria. Tumours vary from 0.5 cm to 11 cm diameter and are spherical or ovoid, occasionally with a multinodular pattern [3–7]. They can be distinguished from other gastric mesenchymal tumours based on immunohistochemical or ultrastructural findings [6, 7]. Patients are usually asymptomatic, however, they may present with the symptoms of abdominal pain or discomfort, occult or overt upper gastrointestinal bleeding from the ulceration of the overlying mucosa. A palpable mass may be present when the tumour is larger and predominantly exophytic. Diagnosis is usually delayed owing to subclinical tumour growth. Endoscopic evaluation may be normal or only show non-specific secondary findings such as extrinsic mass effect or ulceration if the schwannoma is mainly exophytic. Furthermore, as occurred in this case, endoscopic biopsy may not be adequate for definite diagnosis because schwannomas are submucosal tumours and mucosal abnormality may be minimal.
In this case, the abdominal mass appeared to be centred in the gastrocolic ligament and its site of origin could not be confirmed initially, although close relation of the tumour with the gastric antrum was depicted, particularly on three-dimensional volumetric MRI. When a large intraabdominal mass is present next to several organs, its exact site of origin cannot be determined based on the location of its epicentre on cross-sectional imaging, as in this case. However, the benign nature of the tumour and its relation to adjacent structures are well delineated on MRI. Although definite diagnosis of digestive tract schwannoma is made by microscopic examination and immunohistochemical staining, cross-sectional imaging, particularly MRI with direct multiplanar imaging capability, is important in defining the exact location and extent of the tumour with displacement of surrounding organs or vessels, providing valuable information for surgical planning. The imaging findings of gastric schwannoma have rarely been documented [6, 8]. Usually they appear as spherical, ovoid or multilobulated solid masses adjacent to gastric wall, hypoechoic on ultrasound, hypodense on CT and show contrast enhancement. They rarely appear cystic, although large tumours may undergo cystic degeneration. Calcification is uncommon.
The MRI appearance of schwannomas arising from cranial or spinal nerves has been well described in the literature, but that of a gastric schwannoma has not been reported previously. Typically, these lesions are sharply demarcated, strongly enhancing tumours, having low to medium signal intensity on T1 weighted images and high signal intensity on T2 weighted images. The MRI findings in our case are consistent with the literature on cranial or spinal nerve schwannomas, except for unenhanced borders surrounding the lobules. Schwannomas should be included in the differential diagnosis of intramural or exophytic gastric masses when imaging findings show a well defined multilobulated solid mass adjacent to the stomach.
Received for publication January 24, 2002.
Accepted for publication March 19, 2002.
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Abstract
Introduction
