The classification of cells by five types of histograms is the simplest and most generally accepted method in current use at M.D. Anderson Cancer Center.
 

	Control: Characterized by a single DNA content peak in the diploid (2c) region.
	Type I : These histograms are characterized by a single DNA content peak in the diploid (2c) region. Only a few cells may deviate from this normal value.
	Type II: This type of histogram is characterized either by one peak in the tetraploid region, or by two peaks, one in the 2c and one in the 4c region. Few, if any, cells will have a DNA content between 2c and 4c, which corresponds to the normal DNA synthesis phase. Only a few cells may be found outside the normal DNA content values; these cells generally have a DNA content in the 8c region.
	Type III : This type of histogram differs from Type II by having a significant number of cells with DNA content value between 2c and 4c. The proportion of these cells, considered as S cells, is used to evaluate the proliferation activity of the cell population.
	Type IV : These histograms reveal a pronounced and irregular aneuploidy with DNA content values between 2c and 6c, or even 8c and more..

Significance: In general, patients with Type I and II histograms have an improved survival rate over patients with Type III and IV histograms. However, in a small number of patients, Auer histogram type may not always be predictive of outcome, (Auer-et al. ANALYTICAL AND QUANTITATIVE CYTOLOGY, 161-165, 1980.)

• Coefficient of Variation (CV) is the standard deviation expressed as a percentage of the mean. 
• DNA Index is the ratio of sample G1 DNA value to the diploid value of the external reference cells. 
• Ploidy Balance (PB) is the percentage of cells in classes 2c, 4c, and 8c less the percentage of cells in other classes. 
• Hyperploidy Degree (DH) or Rare Event Analysis is the percentage of cells having DNA content greater than 5c. 
• Proliferation Index (PI) is the percentage of cells outside the major peaks (MP), not including adjacent peaks. The PI is lower than the S-phase as measured by Flow Cytometry, but is proportional to it. 

• Diploid: Histogram whose principal peak is centered at 2c. 
• Aneuploid: Histogram whose principal peak is not centered at 2c. 
• Tetraploid: Histogram whose principal peak is centered at 4c. 
• Heteroploid: Histogram of cell lines having different ploidy. 
• Hyperploid: Histogram showing cells having a DNA content greater than 5c. 
• Hypoploid: Histogram showing cells having a DNA content less than 2c. 

Note: A sample can present several of these characteristics simultaneously.

• Labeling Index: 
In the case of nuclear immuno-enzymatic labeling, this index is equal to the ratio:    - number of labeled cells/total number of cells

In the case of cytoplasmic immuno-enzymatic labeling, this index is equal to the ratio:    - area of labeled protions/total area of the structures

• Mean Optical Density: 
This index is equivalent to mean labeling concentration; this is the mean of optical densities measured over: 

 - the labeled nuclei in the case of nuclear immuno-enzymatic labeling

- the labeled areas within the structures in the case of cytoplasmic immuno-enzymatic labeling

• Quick Score: 
This index is equal to: labeling index (LI) (x) mean concentration/100
• Low: (LI)=<5%,Intermediate: (LI)=6-14%, High: (LI)=>15% 
For breast cancer in node-negative patients, Ki-67 (LI)>15% has an increased likelihood for relapse or shorter disease free survival. (LI)<5% reflects a low likelihood for relapse. (Reference: Ki-67 Immunostaining in Node-Negative Stage I/II Breast Carcinoma. Aysegul A. Sahin, M. D., et al., Cancer, Vol 68, No. 3 August 1, 1991.)