Stratification of patients by melanoma cell adhesion molecule (MCAM) expression on the basis of risk: implications for sentinel lymph node biopsy.

BACKGROUND

The usual indication for sentinel lymph node biopsy (SLNB) in melanoma is a primary tumour >1mm thickness but under these criteria less than 20% of SLNBs are positive. Of those patients with a negative sentinel node (SN) over 10% will have disease recurrence within 3 years. A more accurate delineation of candidate patients for SLNB and risk profile for negative SN patients is therefore desirable. Melanoma cell adhesion molecule (MCAM) is a predominant cell adhesion molecule of melanomas and its expression has been implicated in tumour progression and metastasis.

AIMS

To compare MCAM expression in primary and metastatic melanoma and to investigate if MCAM expression in patients meeting the criteria for SLNB correlated with patient outcome.

METHODS

Tissue arrays of primary (n=78) and metastatic (n=92) melanomas were constructed from archived paraffin embedded tissue and MCAM expression detected by immunohistochemistry. Staining positivity and intensity were assessed by visual scoring and correlated with clinical outcome.

RESULTS

In patients meeting the current criteria for SLNB, Cox multivariate analysis showed both MCAM expression positivity and intensity were independently predictive of survival (P=0.007) and development of lymph node disease (P=0.01) in primary melanoma over and above established markers of prognosis, such as Breslow thickness. MCAM-negative patients had a 5-year survival of 92% compared with 40% for MCAM positive.

CONCLUSIONS

Measurement of MCAM expression represents a potential method to stratify SLNB patients on the basis of risk. This would have considerable benefits in terms of both cost and patient morbidity.