It must also be underlined that the cells of some clinically extremely aggressive cancers do not have prominent nucleoli (or even do not have them at all), e.g. desmoplastic small round cell tumor (DSRCT) and small cell neuroendocrine carcinoma – in our opinion it may be related with extremely high Ki67 proliferative index and high mitotic rate in the case of these two cancers, which suggests that a high percentage of cancer cell population is in the active phase of mitotic division, which excludes the presence of nucleoli within these cells. This evidence concerns the gene MKI67 and cancer.