Ki67 antigen and PCNA proliferation markers predict survival in anorectal malignant melanoma

Aims: To find a possible correlation of Ki67 antigen and proliferating cell nuclear antigen (PCNA) with prognosis in anorectal malignant melanoma. Methods and results: Thirty patients with anorectal malignant melanoma were studied. The percentage of tumour cells stained for Ki67 and PCNA in paraffin sections was assessed. Mode of treatment (local excision or abdominoperineal resection), depth of tumour invasion, attempt at cure as defined by complete tumour excision and absence of distant metastases at presentation, tumour blood vessel invasion, and tumour necrosis, as well as Ki67 and PCNA, were all correlated with survival. By univariate analysis, PCNA, Ki67, attempt at cure, local excision (and not abdominoperineal resection), and depth of invasion were all significantly associated with longer survival. By multivariate analysis, only PCNA was significantly associated with survival, while Ki67 showed a significant positive correlation with PCNA. With a cut-off point of 40%, patients with lower Ki67 scores showed survival advantage over those with higher Ki67 scores (P = 0.0004). With a cut-off point of 80%, patients with lower PCNA scores showed survival advantage over those with higher PCNA scores (P = 0.0001). The staining for proliferation markers was also associated with depth of tumour invasion. Conclusions: Ki67 and PCNA immunostaining in paraffin sections may be useful for the prediction of survival in patients with anorectal malignant melanoma. Larger studies are needed to confirm our results.