Gastric schwannoma: a case report

Abstract

Introduction

Schwannomas of the gastrointestinal tract are rare, benign tumours of Schwann cell origin, accounting for 2%–6% of gastrointestinal mesenchymal tumours and only 0.2% of gastric neoplasms [1, 2]. The stomach is the most commonly affected site. These tumours are frequently indistinguishable from gastrointestinal stromal tumour (GIST) on imaging and endoscopy, despite GIST being far more prevalent and carrying genuine malignant potential; preoperative misdiagnosis as GIST has been reported in up to 96.7% of cases [3]. Immunohistochemistry is therefore essential for accurate diagnosis, as management and prognosis differ substantially between the two entities [4]. We report a case of gastric schwannoma detected incidentally on surveillance endoscopy, managed by laparoscopic wedge resection, and briefly discuss the lack of consensus around postoperative surveillance for this rare tumour.

Case report

A 74-year-old man was referred after a mid-body gastric lesion was identified incidentally on surveillance gastroscopy performed in the context of prior rectal cancer, treated by proctocolectomy in 2000 and subtotal colectomy with a permanent stoma. His only other past history was dyslipidaemia, managed on rosuvastatin. He was entirely asymptomatic from a gastrointestinal perspective. Endoscopy demonstrated a well-circumscribed, exophytic submucosal mass at the greater curvature of the gastric body, with intact overlying mucosa (Fig. 1).

Open in new tabDownload slide

Contrast-enhanced computed tomography (CT) of the abdomen and pelvis confirmed a 5 cm exophytic mass at the gastric greater curvature with homogeneous enhancement, no luminal obstruction, and no lymphadenopathy, distant lesions, or ascites. Endoscopic ultrasound-guided fine needle aspiration demonstrated a benign spindle cell proliferation favouring schwannoma. The case was discussed at a multidisciplinary team meeting, and laparoscopic local resection was recommended.

The patient underwent laparoscopic partial gastrectomy with intraoperative gastroscopy. The tumour was confirmed at the greater curvature of the gastric mid-body; incidental dense colo-parietal adhesions unrelated to the lesion were left undisturbed. The omentum was mobilised off the greater curvature, tumour location was confirmed endoscopically, the right gastro-epiploic vessel was ligated, and a gastric wedge resection was performed using a laparoscopic stapler, with omentopexy reinforcing the staple line. The specimen was extracted intact within a retrieval bag.

Macroscopically, the specimen measured 75 × 55 × 35 mm, containing a polypoid submucosal mass (65 × 50 × 31 mm) with a 2 mm clear margin. Microscopy showed bland, wavy spindle cells with nuclear palisading, Verocay bodies, and a peritumoural lymphocytic cuff, without necrosis, atypia, or significant mitotic activity. Immunohistochemistry was positive for SRY-box transcription factor 10 (SOX10) and S100 calcium-binding protein (S100) and negative for discovered on GIST-1 (DOG1), CD117 (c-KIT), smooth muscle actin (SMA), and desmin, confirming gastric schwannoma and excluding GIST and leiomyoma. Of six lymph nodes identified, none showed metastatic disease.

The postoperative course was uncomplicated. Diet was progressively titrated from free fluids to a light diet over a 2-day admission, after which he was discharged. At 4-week review, he was asymptomatic, eating, and drinking well, with a well-healed wound and no incisional hernia. Given the absence of a standardised surveillance protocol for this tumour, a conservative plan of endoscopic surveillance at 6 months, then annually for 5 years, was agreed at multidisciplinary team meeting.

Discussion

Gastric schwannomas are typically slow-growing and asymptomatic, often detected incidentally, as in this case [2, 5]. The principal diagnostic challenge is distinguishing them from GIST: both can present as similarly sized submucosal or exophytic masses with overlapping imaging features, although homogeneous enhancement without necrosis or heterogeneity—as seen here—favours schwannoma over high-risk GIST [3]. Definitive diagnosis nonetheless relies on immunohistochemistry: gastric schwannoma is characteristically S100/SOX10 positive and CD117/DOG1/SMA/desmin negative, the inverse of the typical GIST profile [4, 6]. Complete surgical resection, as achieved here, is curative in the great majority of cases, with published series reporting no recurrence at long-term follow-up [6, 7].

No consensus surveillance protocol exists following resection of gastric schwannoma, reflecting the rarity of the diagnosis. Reported approaches range from a single follow-up CT at 1 year with no further routine surveillance [5], to intensive early endoscopic review at 1, 3, 6, and 12 months following endoscopic resection of smaller lesions [8], to periodic clinical review alone in larger surgical series with disease-free outcomes maintained over many years [7]. Extrapolating surveillance intensity from GIST protocols, which are considerably more intensive given genuine recurrence risk, may be disproportionate for a tumour with negligible malignant potential [9]. Our multidisciplinary team adopted a conservative, endoscopy-based schedule balancing early detection of recurrence against the burden of long-term surveillance. This case adds to a limited evidence base and highlights the need for pooled, multicentre data to inform a risk-stratified, consensus surveillance protocol for gastric schwannoma.

Conflicts of interest

None declared.

Funding

None declared.

Consent

Informed consent was obtained from the patient for publication of this case report and accompanying images.

References