Certain viral diseases provoke oncology more than others. Below - about such effective catalysts:
The virus itself is only one of the conditions necessary for the emergence of a tumor.
In short, viruses can live and multiply only in genetically active cells (and they are not always active in the norm). Some viruses are able to “activate” infected cells independently of normal ones, suppressing or bypassing the body's defense processes. As a result, genetic damage accumulates in the affected cells, the cells, despite this, survive (normally they should undergo programmed death - apoptosis). You can read more about how this happens here
As a result, after the accumulation of a critical amount of the necessary mutations, the infected cells become completely autonomous and immortal, that is, they become malignant.