Appearance of malignant melanoma after a non-cutaneous cancer diagnosis.

Background: The aim of this study is to find the associations between malignant melanoma (MM) and other non-cutaneous malignancies and to see whether there are possible correlations between them.
Methods: We analysed a sample of 1720 patients collected by our melanoma database, to identify patients with both MM and non-cutaneous primary cancer (NCC). The incidence rate (IR) included in our database was calculated as the ratio between the observed patients with NCC and those with MM.
Results: A total of 74 patients, with both NCC and MM, were included in our analysis, corresponding to 4.30% of patients with MM present in our melanoma database. After breast cancer (24.3%; IR = 1:4), the most common malignancies were lymphomas (14.8%; IR = 1:4), renal cell carcinoma (13.5%; IR = 1:7), thyroid cancer (9.4%; IR = 1:11), and prostatic carcinoma (8.1%; IR = 1:12), followed by other cancers. Among patients with lymphomas, most patients (72.7%) had a non-Hodgkin lymphoma. Our study shows a high coexistence of multiple malignancies in patients with MM.
Conclusion: Although we cannot definitively confirm a true association between non-skin cancers and MM, we believe that there are sufficient links for further investigation in order to identify new aetiological factors and therapeutic targets for these cancers.