Gastric Schwannoma

Gastric schwannoma is a benign spindle cell tumour of Schwann cell origin arising in the gastric wall. It accounts for about 0.2% of gastric tumours and 4% of gastrointestinal mesenchymal tumours.

Peak age is 50 to 60 years, with a female predominance. Most tumours are found incidentally and are 1 to 6 cm.

It is almost always benign. Recurrence after complete resection is rare and malignant change is exceptional.

Pathophysiology.

Histology shows interlacing spindle cells with a peripheral lymphoid cuff and germinal centres. Cells are strongly S100 and SOX10 positive, and negative for KIT (CD117), DOG1, desmin and smooth muscle actin, which separates it from gastrointestinal stromal tumour.

Often none. Possible features are epigastric discomfort, early satiety, upper gastrointestinal bleeding from central ulceration, anaemia and a palpable mass.

Endoscopy shows a submucosal bulge, sometimes with central ulceration. Endoscopic ultrasound shows a homogeneous hypoechoic mass arising from the muscularis propria (fourth layer), often with a halo. CT shows a well circumscribed, homogeneously enhancing mass. Superficial biopsy is rarely diagnostic, so use fine needle biopsy with immunohistochemistry.

Differential diagnosis.

• Gastrointestinal stromal tumour.
• Leiomyoma.
• Neuroendocrine tumour.
• Glomus tumour.
• Ectopic pancreas.

Because the tumour cannot be separated from gastrointestinal stromal tumour without tissue, resect tumours that are symptomatic, over 2 cm or growing. Laparoscopic wedge resection with clear margins is usual, with no lymphadenectomy and no adjuvant therapy. Small, asymptomatic lesions with typical immunohistochemistry can be observed.

Monitoring. Endoscopic ultrasound or CT at 6 to 12 months and then every 1 to 2 years for lesions under observation. After complete resection, clinical review and imaging at 1 year.

Referral and escalation. Upper gastrointestinal surgeon and pathologist for immunohistochemistry review.