HMB-45 (anti-gp100)

This monoclonal antibody identifies immature melanosomes.

Immunohistochemical expression

There is positive staining of:

• activated and neoplastic melanocytes

• amelanotic cellular blue nevus: 7/84

• other neural crest tumours

• normal breast epithelium and some breast carcinomas2

• normal sweat glands and some sweat gland tumours3

• angiomyolipomas

• other lesions of the tuberous-sclerosis complex including lymphangioleiomyomatosis1.

• clear cell tumour of the lung ("sugar tumour")1.

• occasional carcinomas

• some myelomas

• some uterine leiomyomas: 9/25(10% or less of cells in 6/11 poorly differentiated and 3/14 well differentiated)5

Diagnostic utility

It shows greater specificity for the identification of malignant melanomas than do S-100 or NKI/C3.  However, the sensitivity, particularly in metastatic melanoma, is somewhat less than 90%.

References

1 Spencer's Pulmonary Pathology, 5th edition, page 973.

2 Bonetti F et al. Breast carcinoma positive for the melanoma marker (HMB45). HMB45 immunoreactivity in normal and neoplastic breast. Am J Clin Pathol 1989;92:91-95.

3 Kanitakis, J., Hermier, C., Chouvet, B. and Thivolet, J. Reactivity of HMB-45 monoclonal antibody with sweat-gland tumours of the skin. Acta Derm Venereol 1991;71:426-8.

4 Zembowicz, A., Granter, S.R., McKee, P.H. and Mihm, M.C. Amelanotic cellular blue nevus: a hypopigmented variant of the cellular blue nevus: clinicopathologic analysis of 20 cases. Am J Surg Pathol 2002;26:1493-500.

5 Simpson KW,Albores-Saavedra J HMB-45 reactivity in conventional uterine leiomyosarcomas. Am J Surg Pathol 2007; 31:95-8

©SMUHT/PW Bishop