Mitotic modifications and aberrations in human cervical cancer

Mitotic modifications and aberrations characteristic of human malignant tumors have been analyzed and illustrated in cervical cancer. Most of them can be explained by assuming that the coordination of the centrosomal and chromosomal mechanisms, typical of normal mitosis, is disturbed. When the spindle mechanism is ahead of the chromosomes, the prophase is relatively shortened. This expresses itself in an increase of the ratio of metaphases to prophases (M/P), which in normal tissues is around 1. With M/P values of 4-6, the first tripolar metaphases are formed, and with higher ratios, divisions having more and more poles appear. The spindle and the chromosomes are out of step in the opposite direction in endocycles, in which the spindle is slowed down or absent. The most common of the endocycles is endoreduplication, followed by endomitosis, which is found in more than half of the cervical cancers. Mitotic abnormalities include lagging chromosomes in metaphase and anaphase and bridges in anaphase, which, when numerous, may lead to restitution. More sporadically occurring are C-mitosis and other abnormalities, including cell and nuclear fusions. There is a wide range of variation in the occurrence and frequency of chromocenters within a tumor, and an even greater variation between tumors. About one-fifth of cervical cancers lack X chromatin bodies. The abnormal chromosome constitutions in cancer are the result of various mitotic modifications and aberrations, as well as chromosome rearrangements. New chromosome combinations are constantly created and selection promotes the fastest dividing ones, which, in turn, become new stem lines of the tumor.