Prognostic value of MMP-2 immunoreactive protein (72 kD type IV collagenase) in primary skin melanoma

The penetration of the subepithelial basement membrane is the first critical step in the dissemination of melanoma. In vitro studies have suggested that the 72 kD type IV collagenase (MMP‐2) may be important in melanoma invasion. It has recently been demonstrated that the expression of MMP‐2 immunoreactive protein increased with increasing atypia in melanocytic tumours and was associated with later haematogenous metastases in melanoma. This paper investigates the value of MMP‐2 as a possible prognostic marker in melanoma. The expression of MMP‐2 immunoreactive protein was studied with immunoperoxidase staining in paraffin‐embedded sections of 50 cases of primary skin melanoma by using specific, affinity purified antibodies. Positive immunostaining was quantified by counting the percentage of positive cancer cells and was compared with clinical patient characteristics and survival. Sixty‐four per cent of the primary melanoma cases displayed positive cytoplasmic immunostaining for MMP‐2 in tumour cells. Marked overexpression of MMP‐2 protein (≥34 per cent of melanoma cells positive) correlated with the 5‐year survival of the patients when compared with patients with lower MMP‐2 positivity, 55 per cent vs. 85 per cent, respectively (P