Mucosal Benign Epithelioid Nerve Sheath Tumours

Definition

A subset of mucosal nerve sheath tumours characterised by the presence of small epithelioid cells. Such tumours occur in both colorectum and bladder1. Epithelioid Schwannomas have also been described in soft tissues.

Epidemiology

There is no association with neurofibromatosis1.

Macroscopic appearances

The colonic tumours form small polyps. The lesions are located in the lamina propria and submucosa.

Histopathology

Margins vary from encapsulated to pushing to infiltrative. There is a combination of spindle and epithelioid cells. The round to oval nuclei show intranuclear pseudoinclusions. The cytoplasm is eosinophilic and fibrillary. Mitoses are not a feature. There may be an infiltrate of eosinophils. The lesions do not clearly show the characteristics of either Schwannomas or neurofibromas.

Immunohistochemistry

	S-100	7/71
	CD34	3/51
	CD117	0/51
	Calretinin	0/51
	EMA	0/11

Differential diagnosis

Gastrointestinal stromal tumour
Neuroblastoma-like neurilemmoma: the lymphocytoid cells have scant cytoplasm and form rosettes.
Perineuroma: positive for EMA but negative for S-100.
Leiomyoma: positive for desmin, calponin and caldesmon but negative for S-100.
Metastatic melanoma

Prognosis

These tumours are benign.

References

1 Lewin MR, Dilworth HP, Abu Alfa AK, et al. Mucosal benign epithelioid nerve sheath tumors. Am J Surg Pathol 2005; 29:1310-5

This page last revised 3.5.2006.