P53-PROTEIN AND KI-67-ANTIGEN EXPRESSION ARE BOTH RELIABLE BIOMARKERSOF PROGNOSIS IN THICK STAGE-I NODULAR MELANOMAS OF THE SKIN

The maximum tumour thickness is the most important prognostic factor i n malignant melanomas of the skin. However, the clinical outcome of th ick nodular melanomas remains unpredictable. Therefore, we investigate d possible prognostic markers in this subset of melanomas. From a mela noma data base, 12 patients with thick ( >3 mm) stage I nodular melano mas of the skin were identified, who were still without signs of progr ession after five years of follow-up. These tumours were compared to a randomly selected series of 12 cases, who did not survive the first f ive years after removal of the tumours. We performed immunostaining fo r the p53-protein and the proliferation associated Ki-67-antigen. For quantification of immunostaining the tumours were entirely scanned. In addition, all tumours were investigated for any differences with conv entionally applied prognostic features: the tumour thickness; the leve l of invasion; the prognostic index (tumour thickness multiplied by mi totic count): and the mean volume-weighted mean nuclear volume. We dem onstrated significant differences between survivors and non-survivors exclusively in respect of the staining-indices for p53 and Ki-67 (P <0 .03 and 0.02, respectively). With both antibodies the tumours of survi vors showed lower counts as compared to nonsurvivors. However, within both groups we found no significant correlations between the p53- and Ki-67-staining results. We conclude that immunostaining for p53-protei n and Ki-67-antigen is helpful to identify individuals with thick nodu lar melanomas who are at risk of metastatic disease.