Enzyme activity measurements are of great relevance to the classification and biochemical characterization of the various types of
leukemias, but they have been much less studied in solid lymphoid
tumors. The authors report investigations in human
lymphomas. The levels of the following
enzymes were determined:
terminal deoxynucleotidyl transferase (TdT),
deoxyribonucleic acid polymerase alpha (DP alpha),
adenosine deaminase (ADA),
purine nucleoside phosphorylase (PNP),
thymidine and
uridine kinases (TK and UK, respectively), and
thymidine phosphorylase (ThPh). Moreover, cytochemical investigations were done in the group of
Burkitt's lymphoma (BL) and
lymphoblastic lymphoma (LL), and ultrastructural studies were performed in seven of the nine LL of this series. These results were obtained: (1) TdT (90 cases) was highly specific for LL; eight of nine LL were positive, and all other histologic types were negative; the only TdT-,
acid esterase (AcE) positive, nonconvoluted LL was probably related to TdT- normal medullary thymocytes, and had an unfavorable
clinical course with resistance to a
vincristine-and-
prednisone-including treatment; (2) ADA (61 cases) could distinguish clearly between the high levels of LL and the low levels found in any other group of
lymphomas; among LL, the highest values were found in T-cell-derived
neoplasias, and the lowest value in a
periodic acid-Schiff (PAS) positive,
acid phosphatase negative case that showed the presence of large nucleoli at the ultrastructural analysis, a finding that is unusual for LL and possibly related to a more immature differentiation stage; (3) PNP (39 cases) values alone were not clinically relevant, but together with ADA levels, a subset of T-LL with high ADA:PNP ratio could be selected among LL; (4) DP alpha (61 cases), and TK and UK (37 cases) were found in concentrations reflecting the
malignancy of the
non-Hodgkin's lymphoma, and were more elevated in the high-grade
malignant lymphomas; (5) ThPh (34 cases) was always elevated in
Hodgkin's disease, but low in
Burkitt's lymphoma and LL; thus, they had a high TK:ThPh ratio that could be useful in predicting clinical response to
thymidine treatment. The authors think that taken together, multiple
enzyme determinations could be useful in the characterization of human
lymphomas.