A method for measuring DNA in tissue cells by flow cytometry utilizing a one step combination nuclear isolation‐DNA fluorochrome staining procedure is described. A variety of cells and tissues, both in vivo and in vitro, was used to illustrate the universal nature of this technique. These included murine bone marrow, liver testicle, sarcoma brain tumor, rat pancreatic islets, human peripheral blood, colon mucosa, colon cancer, sarcoma and brain tumor tissues. A special nuclear isolation medium, which contained either of the DNA fluorochromes, 4′,6‐diamidino‐2 phenylindole‐2 HCl or propidium iodide, was utilized successfully to isolate single suspensions of DNA fluorochrome stained nuclei in a rapid (5–10 min), consistent manner from a variety of tissues and cells. Multiple sampling of the same tissue or comparison between whole tissues and their single cell isolates showed that a representative sample was being obtained.

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In a series of 227 women with endometrial carcinoma stages I-IV the prognostic value of nuclear morphometry and DNA analysis was evaluated prospectively. The tumors were also classified according to histologic subtype, degree of differentiation (FIGO), and nuclear grade. The DNA analysis (ploidy and S-phase fraction) was made using flow cytometry on fresh-frozen tissue. The morphometric measurements and the grading of the tumors were done on both fresh-frozen tissue and on formalin-fixed and paraffin-embedded tissue. The rate of recurrence for the complete series was 14% with 2.2% vaginal metastases. The overall 5-year survival rate was 68% and the corrected survival rate 76%. The minimum nuclear diameter and the standard deviation (SD) of the maximum nuclear diameter were significant and independent prognostic variables in a Cox multivariate analysis when analyzed on paraffin-embedded tissue. The nuclear grade was the single most prognostically informative variable. A corresponding analysis on fresh-frozen tissue showed that the S-phase fraction and the FIGO grading of the tumor were significant variables. The morphometric variables and the nuclear grading were non-significant prognostic variables. Morphologic changes in tumor cell nuclei during the freezing and thawing procedures may explain the loss of prognostic information. A combination of DNA index (fresh-frozen tissue) and the mean values of the shortest nuclear diameter and the SD of the longest diameter (paraffin-embedded tissue) gave the best prognostic information vis-a-vis cancer-related death in an all-possible-subsets regression analysis.