Schwannoma of stomach: a clinicopathologic study of 12 cases

We analyzed clinicopathologically 12 gastric schwannomas. Patient ages ranged from 41 to 79 years (mean, 52 years; median, 59 years). They variably presented with gastric discomfort, bleeding, or rarely gastric outlet obstruction and many were incidental findings during other medical procedures. The maximum tumor diameters ranged from 1.0 to 5.4 cm (mean, 3.5 cm; median 3.8 cm). The typical histologic features included spindle cells with micro-trabecular architecture, focal nuclear atypia, and peritumoral lymphoid cuff. Median mitotic count was 1/50 high-power field. No malignant variants were recognized, and follow-up did not reveal recurrences or metastases. Immunohistochemically, all tumors were positive for S100 and SOX10, and most were also GFAP positive, whereas CD34 and NF were rarely positive. All tumors were negative for cytokeratin AE1/3, HMB45, c-kit, DOG1, smooth muscle actin, desmin, and synaptophysin. None of the tumors showed gastrointestinal stromal tumor-specific KIT or PDGFRA mutations. Gastric schwannoma is a distinctive form of peripheral nerve sheath tumor and it should be distinguished from gastrointestinal stromal tumor and other mesenchymal tumors of the gastrointestinal tract, especially clear cell sarcoma and metastatic melanoma.