Classic Schwannoma of the gastrointestinal tract

Schwannomas occur most often in the stomach but also in the oesophagus and colorectum, rarely in the small intestine. They account for about 3% of gastrointestinal mesenchymal tumours.

Epidemiology

These tumours occur over a wide age range.

Macroscopic appearances

Most tumours are located in the muscularis propria.

Histopathology

The tumours are non-encapsulated . In most cases they are well circumscribed but some tumours merge with the surrounding smooth muscle. There is a surrounding lymphoid cuff which may include germinal centres: this seems to be a distinctive feature. The tumour cells are spindled, in some cases with foci of epithelioid cells. There are rare epithelioid and plexiform variants. Nuclear palisading is vague or absent: this observation has also been made on those nerve sheath tumours occurring with the mucosa.

Immunohistochemistry

Ultrastructure

The spindle cells have interdigitating processes. A basement membrane surrounds many of the cell processes.

Cytogenetics and molecular genetics

There is no c-kit mutation.

Differential diagnosis

• GIST: positive for CD117, CD34 and nestin but negative for GFAP.

• Leiomyomas: positive for muscle markers.

• Microcystic/reticular Schwannoma: most commonly found in the gastrointestinal tract: shows a predominance of a characteristic microcystic or reticualr pattern of cells around myxoid stroma.

Prognosis

These tumours are almost always benign.

References

1 Hou YY, Tan YS, Xu JF, et al. Schwannoma of the gastrointestinal tract: a clinicopathological, immunohistochemical and ultrastructural study of 33 cases. Histopathology 2006; 48:536-45

This page last revised 10.4.2006.

©SMUHT/PW Bishop