Schwannoma of the gastrointestinal tract: a clinicopathological, immunohistochemical and ultrastructural study of 33 cases

Aims: Thirty-three cases of gastrointestinal schwannomas were analysed to elucidate their peculiar clinicopathological, immunohistochemical and ultrastructural features. Methods and results: The patients were 16 men and 17 women, whose ages ranged from 27 to 81 years (median 52.6 years). Tumour size ranged from 10 to 120 mm in diameter. Follow-up in 23 cases from 6 months to 13 years showed no recurrences or metastases. Microscopically, all tumours were composed of spindle cells with focal epithelioid cells in four cases. In all cases except one, there were peripheral cuff-like lymphoid aggregates. Immunohistochemically, tumours were strongly positive for S100 protein and vimentin, the tumours were variably positive for nestin (78.8%, 26/33) and glial fibrillary acidic protein (63.6%, 21/33), three tumours had CD34+ cells, but all were negative for CD117, alpha-smooth muscle actin and desmin. Ultrastructurally, the tumours were composed of elongated spindle shaped cells with prominent parallel membranous structures. Conclusions: Gastrointestinal schwannomas have characteristic histological features, especially the presence of a lymphoid cuff, that are different from their soft tissue and central nervous system counterparts. Gastrointestinal tract schwannomas behave in a benign fashion.