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Schwannoma of the stomach: a case report
© Singh et al. 2016
Received: 12 March 2015
Accepted: 8 December 2015
Published: 15 January 2016
Schwannomas, also known as neurilemmomas, are benign slow-growing neoplasms originating from a Schwann cell sheath. These neoplasms are rare among the mesenchymal tumors of the gastrointestinal tract. In the stomach, Schwannomas only represent 0.2 % of all gastric tumors; this makes the presentation of a schwannoma in the stomach of a man in his seventh decade unusual. This case report highlights the rarity of a schwannoma at the greater curvature of the stomach because only a few cases have been reported in the literature. This case describes the importance of including gastric schwannomas in the differential diagnosis when preoperative assessment reveals a submucosal gastric mass with gastrointestinal stromal tumor as a leading differential diagnosis because of its common occurrence at this site.
A 72-year-old man of Indian origin presented with a painless abdominal mass with nonspecific gastrointestinal upset. An endoscopy showed a submucosal lesion in his stomach measuring 4×3×2 cm. Histology revealed a benign spindle cell tumor. Immunohistochemistry confirmed the diagnosis of gastric schwannoma. He is on regular follow-up and doing well.
It should be remembered that a schwannoma can present as a mass lesion in the stomach and mimic gastrointestinal stromal tumor. Patients should undergo an endoscopy and a biopsy of the lesion should be done. Many patients do not undergo endoscopy which can delay diagnosis and management. As these tumors have an excellent prognosis, surgical removal is sufficient treatment. Surgeons, radiologists, pathologists and gastroenterologists must be aware of this entity.
Schwannomas, also known as neurilemmomas, are benign slow-growing neoplasms originating from a Schwann cell sheath. These neoplasms are rare among the mesenchymal tumors of the gastrointestinal tract but develop most commonly in the stomach representing 0.2 % of all gastric tumors [1–6]. The main differential diagnosis of a gastric submucosal schwannoma is a gastrointestinal stromal tumor (GIST). However, treatment and prognosis for gastric schwannomas and GISTs vary because gastric schwannomas have an excellent prognosis because of their benign nature whereas 10 to 30 % of GISTs can have malignant behavior with common recurrences. Malignant schwannomas of the stomach are extremely rare. Hence, it is important to make an accurate diagnosis for proper treatment options as medical management is available in the form of imatinib for GIST as compared to schwannoma, as well as surgical intervention in both [6, 7]. Patients can present with bleeding or a palpable mass. Schwannomas present as submucosal tumors and diagnosis is based on histological features and positivity for S-100 and negativity for smooth muscle actin (SMA) and c-Kit [3, 6–8]. As these tumors have an excellent prognosis, surgical removal is sufficient treatment.
The vast majority of spindle cell stromal tumors of the gastrointestinal tract were once considered to originate from smooth muscle. With the development of immunohistochemical staining and electron microscopy various distinct origins have become apparent. These have allowed for a more precise classification among stromal tumors of the gastrointestinal tract. The most common gastrointestinal site is the stomach. Schwannomas constitute 0.2 % of all gastric neoplasms . Malignant transformation of a gastric schwannoma is very rare. These tumors arise from the fundus, body or antrum of the stomach and are commonly intramural. Tumors can vary from 0.5 to 11 cm in diameter. Schwannomas tend to present in the fifth to sixth decades of life and more commonly in females. They are usually asymptomatic and can be discovered incidentally. They are usually solitary lesions arising from the lesser curvature of the stomach [2–4]; however, in our case it was the greater curvature. The most common presenting symptom can be upper gastrointestinal bleeding and abdominal discomfort. On a CT scan, a gastric schwannoma tends to be homogenous, which distinguishes it from leiomyomas and leiomyosarcomas. Magnetic resonance imaging (MRI) can determine the exact layer of origin and location of the tumor . The typical endoscopic appearance of gastric schwannoma is a round protruding submucosal mass with overlying ulcerated mucosa which is usually seen in patients with a history of gastrointestinal bleeding. In our case, an initial biopsy revealed only mucosal tissue; false-negative results of an endoscopic biopsy can be given because normal mucosa overlies the submucosal lesion. On pathological examination the tumors are encased by intact mucosa and they principally involve submucosa and muscularis propria. These tumors have spindle-shaped nuclei and have a fascicular arrangement. No mitosis/necrosis/significant nuclear pleomorphism are seen. A diffuse and intense positivity for vimentin and S-100 protein is detected. Gastric malignant schwannomas can be distinguished from benign schwannomas on the basis of histological examination of the resected specimens, not by clinical symptoms or imaging studies [3, 9–11]. The treatment options for gastric schwannoma are the same regardless of whether the tumor is benign or has malignant potential. Thus, surgical resection is the only possible treatment for gastric schwannoma as compared to GIST where larger tumors necessitate subtotal or total gastrectomy [12, 13].
It should be remembered that a schwannoma can present as a mass lesion in the stomach and can mimic GIST. Many patients do not undergo endoscopy which can delay diagnosis and management. As these tumors have an excellent prognosis, surgical removal in the form of wedge resection, subtotal resection or near-total resection is sufficient treatment. The prognosis for patients with a solitary schwannoma of the stomach following resection is very good. Surgeons, radiologists, pathologists and gastroenterologists must be aware that although gastric schwannomas are rare among spindle cell tumors of the gastrointestinal tract, diagnosis should always be confirmed by IHC and GISTs should be ruled out. Although malignant transformation can occur, it is very rare. Recurrent disease is generally associated with an incomplete surgical margin. The use of molecular therapy for gastric schwannoma is not clearly established yet.
Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
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