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.