Changes in lactate dehydrogenase isoenzyme pattern in patients with tumors of the central nervous system.

Lactate dehydrogenase (LDH) isoenzymes were studied in biopsy samples obtained from 100 benign and malignant brain tumors. Diagnosis was confirmed by histopathology. It is observed that all tumors investigated had elevated LDH activity and showed a LDH isoenzyme pattern which is different from that of normal brain. A pronounced cathodal shift was seen in malignant tumors like medulloblastoma, grade 3-4 astrocytomas and neuroblastomas, whereas anodal pattern was seen in benign tumors like grade 1-2 astrocytomas and oligodendrogliomas. Some tumors like meningiomas showed a midzone pattern like increased LDH3. It was possible to differentiate certain tumors on the basis of LDH isoenzyme pattern like medulloblastomas into differentiated and undifferentiated; craniopharyngiomas into recurring and non-recurring ones. LDH1/LDH5 ratio was low (< 1.0) in malignant tumors and high (5.0-14.0) in benign tumors and it was useful in differentiating tumors according to the degree of malignancy and biological behavior. It is observed that both LDH isoenzyme pattern and LDH1/LDH5 ratio could be used as an adjuvant to histopathological grading of brain tumors.