Gastric Pyloric Schwannoma: A Case Report and Review of the Literature

Abstract Introduction Schwannomas are slow-growing, subclinical neoplasms rarely found in the gastrointestinal tract. This study reports a schwannoma in the pyloric region of the stomach. Case presentation A 50-year-old female presented with a one-week history of epigastric pain, dark tarry stools, and nausea. Endoscopic examination and biopsy confirmed the diagnosis of gastric schwannoma. The patient underwent surgical resection of the tumor. Histopathological examination showed benign spindle cells with strong S100 positivity, confirming schwannoma. Post-operative follow-up included treatment for H. pylori infection and monitoring for recurrence or complications. No recurrence was reported after six months. Literature Review Gastric schwannoma is challenging to distinguish from other submucosal tumors preoperatively. Reviews of recent case reports indicate the importance of detailed imaging in diagnosis, and surgical resection remains the treatment of choice, with an excellent prognosis and low recurrence rates. Conclusion Schwannoma is rare in the stomach, especially in the pyloric region. Definitive diagnosis may require immunohistochemical analysis. Appropriate follow-up after treatment can be essential to identify emerging complications and ensure timely intervention. Introduction Schwannomas, also referred to as neurilemmomas or neurinomas, are uncommon and non-cancerous spindle cell tumors that originate from excessive proliferation of myelin-producing Schwann cells in the nerve sheath and remain localized in their primary location [1,2]. They are frequently slow-growing and rarely found in the gastrointestinal tract (GIT). Gastric schwannoma (GS) represents only 2–6% of mesenchymal tumors within the GIT and 0.2% of all gastric tumors [3,4]. Although most schwannomas occur alone, GS is often part of neurofibromatosis type 2 and has an association with other tumors. There is a gender predilection towards females [3]. Preoperatively, GS is often challenging to accurately distinguish from gastric submucosal or other stromal tumors due to physicians' limited recognition of GS [5,6]. Herein, a case of schwannoma originating from the pyloric region of the stomach is reported. The references’ eligibility has been verified, and the report has been structured in accordance with CaReL guidelines [7,8]. Case Presentation Patient information A 50-year-old female presented with epigastric pain for one week. The pain was associated with melena and nausea, with no constipation, diarrhea, or fever. Her past medical history was negative for any chronic disease. She had a thyroid lobectomy two years ago and was on thyroxin 100 mcg/day. Clinical findings Only epigastric tenderness was noted on physical examination, with no other systemic abnormalities. Diagnostic assessment An abdominal ultrasound (U/S) showed a well-defined hypoechoic mass (30 mm) in the pyloric region of the stomach. A contrast-enhanced computed tomography (CT) scan of the abdomen revealed a well-defined, smooth outline lesion measuring 35x30 mm in the pyloric region with mild mucosal wall thickening (7 mm) and relative proximal dilation of the stomach, without lymphadenopathy. A dynamic magnetic resonance imaging (MRI) of the abdomen revealed a well-defined, 33 x 27 x 27 mm, space-occupying lesion in the epigastric region between the lesser curvature of the stomach and the left hepatic lobe. The mass exhibited T1 hypointensity, T2 hyperintensity, restricted diffusion on diffusion-weighted imaging, and diffuse early enhancement with retained contrast in the delayed phase. The mass was attached to the stomach wall (Figure 1). An esophagogastroduodenoscopy (EGD) revealed a large subepithelial lesion, approximately 4 cm, located in the incisura and extending to the lower body on the lesser curvature side, with an antral nipple sign. The overlying mucosa was normal, but there was nodular antral gastropathy. Therapeutic intervention A resection of the anterior gastric wall near the incisura angularis was performed to remove the mass. Histopathological examination of the lesion revealed hypo- and hypercellular areas of spindled cells arranged in loose fascicles and having neural-type, lightly eosinophilic and clear cytoplasm and spindled and buckled nuclei with fine chromatin. Scattered hyalinized blood vessels were present within the lesion. These findings indicated a benign spindle cell lesion suggestive of schwannoma. The tumor had a mitotic rate of less than five mitoses per 50 high-power fields. There was necrosis or vascular invasion, and the resection margins were free. Four lymph nodes were examined and found to be negative for metastasis (Figure 2). Immunohistochemistry of the tumor revealed positivity for S100, characterized by strong and diffuse cytoplasmic and nuclear staining. Weak and focal cytoplasmic staining was observed for desmin and smooth muscle actin, while the tumor was negative for CD117 and CD34. Follow-up and Outcome Six months postoperatively, the patient developed lower back pain. Lumbosacral MRI showed L3-4 and L4-5 mild disc thecal sac indentation, causing mild bilateral foraminal narrowing and a focal bone lesion at the acetabular root. Pelvic MRI indicated early osteoarthritis changes in the right hip joint with subchondral pseudocystic changes at the acetabular roof. It also showed a thin-walled unilocular cystic lesion in the left ovary measuring 40x20 mm. The patient received analgesics for disc problems and osteoarthritis. A follow-up EGD one year later revealed a long transverse scar in the incisura area and mucosal congestion. Multiple biopsies from the area showed chronic active H. pylori pangastritis without metaplastic and dysplastic changes. The patient was referred to a gastroenterologist and started a regimen for H. pylori eradication. Subsequently, a CT scan revealed a thickening of the gastric outlet and pyloric wall. The rest of the stomach was distended and fluid-filled, raising suspicion of a gastric ulcer. An endoscopic biopsy from the gastric mucosa revealed mild chronic gastritis with mild glandular atrophy, ulceration, and fibromuscular hyperplasia, with no evidence of H. pylori microorganisms, intestinal metaplasia, or dysplasia. A biopsy was also taken from a small mid-esophageal ulcer, which showed no pathologic findings. Discussion Gastric schwannomas are rare mesenchymal benign tumors, comprising 0.2% of all gastric tumors [4]. Malignant transformation of GS is extremely rare [9]. The development of GS can occur at any age, but it is most commonly found in individuals in their fifties and sixties, with a higher incidence in women. Although many GSs are discovered incidentally, they may cause nonspecific symptoms such as pain or GIT bleeding [6]. In reviewing eight cases of GS, four cases presented with abdominal pain or discomfort, two had a palpable abdominal mass, one had hematochezia, and another one had weight loss and early satiety (Table 1). The present case was a 50-year-old female who complained about abdominal pain in the epigastric region for a week. Table 1. Review of eight reported cases of gastric schwannoma Author, year [Reference] Study design No. of cases Age (year) Sex Clinical Presentation History Diagnostic Assessment Treatment Follow up-time Recurrence Medical Surgical Mass Location/ Detection method Disease appearance Mass size (mm) Immunohistochemical findings Sorial et al., 2024[1] Case report 1 82 M Abdominal pain N/A N/A GC of the stomach / CT No lesions or ulcers 32 S100 (+). CD34, CD117, DOG-1, DS, & SMA (-) Ki67 (2-3%) SWGR during laparoscopy N/A N/A Majdoubi et al., 2024[3] Case report 1 50 M Persistent postprandial pain, melena, anorexia, asthenia None None Fundic region along the GC/ CT, GI endoscopy Peptic ulcer and lesion 33 Fusiform cells. CD 117 (-) S100 (+) DOG (-) DS (-) AML (-) Laparoscopic gastric atypical resection 8 months No Manjesh et al., 2024[4] Case report 1 62 F Early satiety, weight loss N/A N/A Fundus / USG, upper GI endoscopy, CECT Hypoechoic mass 83 Spindle cells. S100, GFAP, & P16 (+). CD117, DOG-1, SMA, & CD34 (-) Exploratory laparotomy & Excision N/A N/A Huang et al., 2024[5] Case report 1 72 F Abdominal distension N/A N/A Anterior lower stomach near GC / EUS, CT, EG White ulcer scar 55 S-100, SDHB, & SOX-10 (+) CD34, CD117, DOG-1, & DS (−). Ki67 (1%) EFTR 1 week No Kostovski et al., 2024[6] Case report 1 68 M Lower abdominal discomfort None None Antral region along the GC / CECT Submucosal gastric lesion 62 Spindle cells. S100, SDHB, & SOX10, (+). CD34, CD 117, DOG-1, & DS (−). Ki-67 (<1%) Supraumbilical median laparotomy & Excision 1 month No Kormann et al., 2024[10] Case report 1 67 M Progressive fatigue, paleness, hematochezia None N/A Gastric antrum / Upper EUS Submucosal lesion 9 S100 (+) Hybrid ESD-EFTR 1st 6 years No 2nd 3 months after intervention Lin et al., 2024[11] Case report 1 66 F Protruding subepithelial mass N/A N/A Gastric fundus / EGD, EUS, CT Subepithelial lesion 25 Short spindle-shaped cells. S100 (+) Laparoscopic surgery N/A N/A Huang et al., 2024[12] Case report 1 31 F Palpable abdominal mass N/A N/A Posterior wall of the GLC/ USG, CT Mucosal ulcer 64 N/A Laparoscopic gastric lesion resection 2 weeks No M: male F: female IDA: iron-deficiency anemia N/A: non-available GC: greater curvature CT: computed tomography GLC: gastric lesser curvature USG: ultrasonography EUS: endoscopic ultrasound EGD: esophagogastroduodenoscopy GI: gastrointestinal CECT: contrast-enhanced computed tomography EG: electrocoagulation mm: millimeter (+): positive (-): negative