Cancer is characterized by genomic complexity and chromosomal instability (CIN). Atypical mitosis and nuclear atypia such as micronuclei have been reported as morphological characteristics of chromosomal instability. An atypical mitotic figure is defined as anything other than the typical form of normal mitosis, including multipolar, ring, dispersed, asymmetrical, and lag-type mitoses. A micronucleus is defined as the small nucleus that forms whenever a chromosome or its fragment is not incorporated into one of the daughter nuclei during cell division. A telomere plays a key role in chromosomal instability. Telomere dysfunction induces fusion of chromatids and chromosome missegregation and this phenomenon can be observed as abnormal mitotic figures and micronuclei. Detection of morphological markers of chromosomal instability using pathological specimens, even small biopsy or cytological specimens, may provide valuable information concerning the prognosis of cancers. Here, we discuss morphological assessment of chromosomal instability using routine pathological specimens.
Part of the book: Chromosomal Abnormalities