The relationship between the intracellular levels of DNA polymerase alpha (DP-alpha), adenosine deaminase (ADA) and lactate dehydrogenase (LDH) and the degree of malignancy of human lymphomas was investigated. Twelve non-neoplastic lymph nodes and 88 malignant lymphomas were examined. For non-Hodgkin's lymphomas (NHL) the low or high grade of malignancy was established according to three classifications: the Rappaport, the Kiel and the Working Formulation for Clinical Usage, with the latter also recognizing an intermediate grade group. Non-neoplastic lymph nodes had significantly lower levels of all the three enzymes than those found in high-grade malignant NHL (the P value ranged from <0.02 to <0.001). Hodgkin's disease, a slowly evolving neoplasia, showed lower levels of DP-alpha (P <0.001) and ADA (P <0.001), but not of LDH, than high-grade NHL. Among NHL, whatever classification was used, the low-grade malignant lymphomas had significantly lower levels than the high-grade ones for all the three enzymes (P <0.005 or P <0.001). The intermediate-grade group of the Working Formulation different from the high-grade group for DP-alpha (P <0.01) and ADA (P <0.02) but not for LDH. It differed from the low-grade group only for ADA (P <0.005). Lymphoblastic and Burkitt's lymphomas were the groups with the highest levels of the three enzymes. Among low-grade lymphomas very low values were found in the histological entities defined as DLWD in the Rappaport classification, CLL and lymphoplasmacytoid immunocytoma in the Kiel classification and small lymphocytic (group A) in the WF. The levels of all enzymes in these histotypes were always significantly different from the other low-grade histotypes, and from the intermediate-grade ones of the WF. In the Kiel classification polymorphous lymphoplasmacytoid lymphoma, recently recognized as a group with a quite aggressive clinical course, was characterized by high levels of all three enzymes. Moreover, among centroblastic-centrocytic (Cb-Cc) lymphomas those associated with a better prognosis (Cb-Cc follicular, with small centrocytes) had lower levels of DP-alpha (P <0.05) than those with a mixed cellular population. Taken together, these data suggest that intracellular enzyme values may have a role in better defining the prognosis of NHL.
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