Clinical Case Discussion

What is Ploidy?

Four types of ploidy are known: diploid, haploid, tetraploid and aneuploid. Ploidy describes the number of complete chromosome sets in a nucleus. For example, a human cell (with the exception of the reproductive cells) has 23 pairs (46 single) of chromosomes in each nucleus, 23 from the mother and 23 from the father. The 46 chromosomes represent 23 pairs, 22 are homologous pairs of autosomes and two sex chromosomes (1). This is known as a diploid number of chromosomes which represents the normal number of chromosomes for humans. The reproductive cell (sperm and ova) each has only 23 chromosomes (one chromosome of each type). This is also normal for the sex cells and is called haploid number of chromosomes.
In humans, a change in the number of chromosomes – from tetraploid to aneuploid -- is considered to be abnormal. This is especially true with aneuploid DNA, which is associated with aggressive behavior and is seen in aggressive malignant neoplasms. Tetraploid DNA has two sets of diploid (four sets of haploid) chromosomes or twice the number of a diploid DNA. Aneuploid DNA represents either an excess or a lack of chromosomes than that of the normal diploid; they are not duplicates of the diploid. Normal diploid cells can go through tetraploid and aneuploid changes during the process of progression to cancer. Diploid can change to aneuploid directly. Cells with aneuploid DNA are usually malignant or have the potential to become malignant. This was the case with the studies published by the Norwegian investigators, who suggested that the genetic aberrations of aneuploid are believed by some to be the cause rather than the consequence of carcinogenesis thus rendering it a significant predictive marker for tumor progression and for prognosis.

Referrences

1. Cotran, Kumar, Collins. Robbin’s Pathologic Basis of Disease. Sixth edition. Saunders.
2. Sudbø J, Ried T et al. Abnormal DNA content predicts the occurrence of carcinomas in non-dysplastic oral white patches. Oral Oncol. 37 (2001), pp. 558–565. SummaryPlus | Full Text + Links | PDF (384 K)
3. Sudbø J, Kildal W et al. DNA content as a prognostic marker in patients with oral leukoplakia. N. Engl. J. Med. 344 (2001), pp. 1270–1278. Full Text via CrossRef