EN
The paper presents a historical outline of studies on tumours from prehistoric times (paleo-oncology) to the present, as well as explains how neoplastic processes developed and why they developed only in multicellular organisms (Metazoa). One of such explanations refers to the development of the body’s defence system in the form of a cellular (inflammatory) infiltrate directed both against exopathogens, e.g. viruses, and against neoplastic cells. The paper also discusses the role of the infiltrate in the primary and secondary neoplastic progression and in regression, as well as the influence of exogenous and endogenous factors, including dissipative factors, on tumour development.