Differences in the histological grade of malignancies may reflect diagnostic quality, that is, averagely earlier or later tumor detection in a given country. Studies of Chernobyl-related renal-cell carcinoma with a control from Spain and Colombia are discussed here in comparison with thyroid cancer research. It is concluded that suppositions about averagely higher grade and enhanced aggressiveness of malignancies from the areas previously contaminated by the Chernobyl fallout are unfounded and can lead to overtreatment. Results of many studies of Chernobyl-related malignancies are valuable; but conclusions should be reassessed taking into account that some cases, classified as aggressive radiogenic cancers, were in fact late-stage neglected malignancies. Associations of various markers with the tumor progression can become a field for the future research and re-interpretation of data obtained in studies comparing malignancies from different countries. Some markers may reflect efficiency of healthcare services.