DNA-grading of malignant lymphomas. I. Prognostic significance, reproducibility and comparison with other classifications.

The prognostic significance of the DNA Malignancy Grade (DNA-MG) was tested for 83 malignant non Hodgkin lymphoma patients in comparison with three different subjective morphological classification systems (New Working Formulation for Clinical Usage, Rappaport and Kiel Classification). Monolayer smears prepared from paraffin embedded tissue and imprint smears from fresh cut lymph-nodes were investigated. Feulgen staining was performed automatically. The scalar DNA-MG was determined by rapid interactive DNA-cytometry, using an automatic microscope and a TV-image analysis system. A strong influence of the DNA-MG on length of survival was found. Compared with morphological classification systems, the DNA-MG was of greater prognostic validity as revealed by different statistical tests. Significant differences of survival probabilities between some groups with differences of 0.5 DNA-MG only were found. The interobserver reproducibility of this new prognostic index was found to be 95% within a range of +/-0.4 DNA-MG.