Abstract:Background/Aims: HCV is a RNA virus that cannot be integrated with the host genome; it can, however, exert its oncogenic potential indirectly by contributing to the modulatory effects of the host immune system, probably through a capacity to elude the immune system. We have carried out a case-controlled study on the different oncological pathologies which have, to date, been shown to have a relationship with HCV. Methods: We screened 495 patients with different types of cancer: 114 cases of liver cancer, 41 of multiple myeloma, 111 non-Hodgkin’s lymphomas, 130 thyroid cancers, 63 cases of Hodgkin’s disease. The controls were 226 patients with no history of cancer. The relationship between each cancer and HCV infection was assessed by means of odds ratios (OR) and corresponding 95% confidence intervals. Results: Risks were greater for liver cancer (OR=32.9 95% CI 16.5–65.4, p<0.0001), multiple myeloma (OR=4.5 95% CI 1.9–10.7, p=0.0004) and B-cell non-Hodgkin’s lymphoma (OR=3.7 95% CI 1.9–7.4, p=0.0001). For Hodgkin’s disease there was no significant association (p=0.3). An association between HCV and thyroid cancer was noted (OR=2.8 95% CI 1.2–6.3, p=0.01). Conlusion: Our study is particularly important for public health since the high prevalence of HCV in the South of Italy gives reason to expect increases in not only liver cancer, but also tumors associated with the immune system and thyroid cancer in years to come.