Correlation of Ki-67 expression in cutaneous primary melanoma with prognosis in a prospective study: Different correlation according to thickness

Background: The proliferative activity of melanoma cells, evaluated as MIB-1 immunoreactivity against a Ki-67 epitope, has been considered an indicator of poor prognosis in thick primary melanomas. Objective: The aim of the study was to assess the correlation between the growth fraction of primary melanomas, assessed by means of Ki-67 immunoreactivity); and metastatic relapse. Methods: Ki-67 reactivity in primary melanomas was evaluated as at least 5%, of positive neoplastic cells and was assessed on fresh specimens of 55 primary lesions at the time of excision. Such reactivity was correlated with metastatic relapse of patients in a prospective stud): by means of multivariate Cox regression models (follow-up, 3-120 months). Results: Ki-67 immunoreactivity was associated with increasing thickness (P =.003). Positive correlation was found between Ki-67 reactivity and metastatic dissemination in primary melanomas less than 1.5 mm chick (n = 23; mean thickness, 0.75 +/- 0.3 mm; P =.002). On the contrary, a negative correlation was found between Ki-67 reactivity and metastatic activity in primary melanomas thicker than 1.5 mm (n = 32; mean thickness, 4.0 +/- 1.6 mm; P =.019). Conclusion: Ki-67 proliferative activity appears to be a possible predictor of metastasis in primary melanomas, in particular, an indicator of poor prognosis in lesions less than 1.5 mm thick.