Neurilemmoma (benign schwannoma)

Immunohistochemistry

• S-100; strongly positive, especially in Antoni A areas

• CD57 (Leu-7)

• GFAP

• Myelin basic protein has given variable results

		retroperitoneal	peripheral
	S-100	90/902	22/22 (peripheral schwannomas)2
	GFAP	104/1152	3/222
	AE1/AE3	71/104 (positivity mainly in Antoni A areas)2	0/222
	34bE12	0/232
	CK1	24/392
	CK4	0/392
	CK5/6	0/112
	CK6	1/242
	CK7	8/612
	Cam 5.2 (CK8/CK18)	0/582
	CK10	0/242
	CK13	0/152
	CK14	3/242
	CK15	0/392
	CK16	0/392
	CK17	0/392
	CK18	0/242
	CK19	0/352
	CK20	0/242
	HMB45	0/1152	0/222

The positivity for cytokeratins may be due to cross reactivity with GFAP.

Cytogenetics

Monosomy 22, eliminating one of the NF-2 alleles, has been reported in Schwannomas, neurofibromas and perineuromas¹.

Differential diagnosis

See the immunohistochemistry of the differential diagnosis of spindle cell tumours of the pleura.

• leiomyoma: may also be positive for S-100 and CD57. Desmin and SMA will be positive.

References

Diagnostic Immunohistochemistry edited by Professor D. J. Dabbs, page 72

¹ Hahn HP, Fletcher CDM. The role of cytogenetics and molecular genetics in soft tissue tumour diagnosis - a realistic approach. Current Diagnsotic Pathology 2005;11:361-370.

² Fanburg-Smith JC, Majidi M,Miettinen M. Keratin expression in schwannoma; a study of 115 retroperitoneal and 22 peripheral schwannomas. Mod Pathol 2006; 19:115-21

©SMUHT/PW Bishop