Endometriosis is a benign proliferative process, where tissues of the uterine mucosa are present ectopically, generally manifesting by infertility and pain. Awareness of similarity between endometriosis and neoplastic process, as well as of oncological risk associated therewith is low. Since 1925, when Sampson was the first to highlight the fact that endometriosis may transform into a malignant lesion, several papers appeared in the medical literature extensively documenting the correlation between endometriosis and tumors, in particular with ovarian cancer. The aim of this paper was to examine correlations linking endometriosis with the neoplastic process by reviewing medical literature published in English in the aspect of epidemiological evidence of endometriosis – cancer correlation, comparison of clinical-pathological features of both entities and comparison of molecular and genetic features of endometriosis with the “cancer phenotype” as defined by Hanahan and Weinberg in their paper The hallmarks of cancer. A large body of evidence has been collected documenting similarity of endometriosis to the neoplastic process, its association with malignant transformation and increased risk of cancer and other malignant tumors. It is not clear, whether endometriotic lesions may undergo malignant transformation directly, indirectly with an intermediate phase, the so-called atypical endometriosis, or endometriosis and cancer possess common initial antecedent mechanisms and/or predisposing factors (e.g. genetic susceptibility, sensitivity to exposure to environmental toxins) with subsequent divergence on the molecular level. Incidence of endometriosis undoubtedly creates an oncological risk, necessitating elucidation by further genetic and molecular studies.