Despite the fact that most studies have found correlationship between DNA ploidy and histopathologic grade of NHL, the role of DNA ploidy as a prognostic factor is unclear. It has been suggested that the lack of signification may be due to the limited power of resolution of flow cytometry DNA quantitation when DNA index is low and there are relatively small numbers of DNA aneuploid cells in the sample. In the studies performed on paraffin-embedded material, which give larger CV, this effect may be magnified, with a decreased sensitivity of the method. The consequence is to artificially overestimate the incidence of DNA diploid cases by underestimating the incidence od DNA aneuploid cases.

We have studied archival samples of 66 patients of NHL. We have investigated the value of DNA ploidy in relation with evolution and prognosis of NHL. The samples of NHL diagnosis blocks were prepared using a modification of the method described by Hedley. Flow Cytometry was performed using an Epics Profile 11. Acquisitiongates were set on the basis of LFW-LSS signals and peak-integrated fluorescent signals (doublet discrimination), 50.000 events were acquired and stored in list mode. The DNA analysis was performed using Multycicle software.

DNA-aneuploidy was detected in 19 cases. The mean G0G1 peak CV was 4,73±1,36%. In all cases bacground and debris (BAD) were <15%. We found a significant increase of DNA aneuploidy in high grade lymphomas, but we did not find any relationship between DNA ploidy and clinic presentation, treatment outcome or survival in the whole group of patients. However, in the 28 high grade NHL, the DNA aneuploid tumors gave a worse treatment response with a significant lower percentage of complete remission (p=0,024). Only DNA ploidy was useful to predict treatment response in high grade lymphomas that were identically treated. S phase was found to be an independent prognostic factor. Patients with a S phase >9% have poor vital prognostic (p=0,038). In low grade NHL, a S phase >7% was associated with a short survival (p=0,040).

We agree that DNA flow cytometry in neoplastic hemopathology should be preferentially performed on fresh specimens, but in NHL the study of archival material, if the CV and BAD are low, may be a valid alternative for DNA analysis and that could provide prognostic information of treatment response and survival in clinic and histopathologic homogeneous groups.