Neuroendocrine secretory protein-55, NESP-55

NESP-55 is a member of the chromogranin family. It is encoded by the GNAS1 gene on chromosome 20 at 20q13. Genetic imprinting ensures that only the maternal allele is expressed. NESP-55 is expressed in the large dense core granules of the adrenal medulla, anterior and posterior pituitary and within the brain¹.

Immunohistochemical expression

	NESP-55	Chromogranin A	Chromogranin B	Secretogranin II
Pulmonary typical carcinoids	1/15 (this one case showed positivity of <5% of cells)1	14/151	14/14 (including positivity in one case negative for chromogranin A)1	14/141
Ileal typical carcinoid	0/111	11/111	10/101	9/101
Gastric typical carcinoid	0/41	4/41	3/31	2/31
Rectal typical carcinoid	1/4 (this one case showed positivity of <5% of cells)1	1/41	4/41	4/41
Pancreatic endocrine tumour	14/191	19/191	18/181	18/181
Adrenal phaeochromocytoma	10/101	10/101	6/61	6/61

NESP-55 shows granular cytoplasmic staining with perinuclear accentuation¹.

NESP-55 may stain benign pancreatic endocrine tumours more strongly than malignant tumours:

		Diffuse	Focal
Functional	Insulinoma	5/6	1/6
	Gastrinoma	0/2	2/2
	VIPoma	0/1	1/1
	Glucagonoma	0/1	0/1
	Acromegaly	0/1	0/1
Non-functional		1/7	4/7
No metastases		6/12	5/12
With metastases		0/7	3/7

Diagnostic utility

• Differentiation of pheochromocytomas and pancreatic endocrine tumours (positive for NESP-55) from pulmonary, gastric, ileal and rectal carcinoids (negative for NESP-55).

• Possibly in the differentiation of benign (positive) from malignant (negative) pancreatic endocrine tumours: this contradicts the proposed use to identify the site of origin of a metastatic neuroendocrine tumour.

References

¹Srivastava, A., O. Padilla, et al. (2004). "Neuroendocrine secretory protein-55 (NESP-55) expression discriminates pancreatic endocrine tumors and pheochromocytomas from gastrointestinal and pulmonary carcinoids." Am J Surg Pathol 28(10): 1371-8.

²Fahrenkamp, A. G., C. Wibbeke, et al. (1995). "Immunohistochemical distribution of chromogranins A and B and secretogranin II in neuroendocrine tumours of the gastrointestinal tract." Virchows Arch 426(4): 361-7.

This page last revised 18.11.2004.

©SMUHT/PW Bishop