Elevation of serum lactic dehydrogenase levels as an early marker of occult malignant lymphoma.

Elevated serum lactic dehydrogenase (LDH) levels, 595 to 615 microns/ml (normal less than 225 microns/ml) with predominance of LDH isoenzymes 2 and 3 was the early and only sign of occult malignant lymphoma in three patients. In the first patient, overt lymphoma appeared clinically only 2 months after the finding of elevated serum LDH levels, whereas in the other two asymptomatic patients, pathologic LDH levels were the only clues to the need for further diagnostic investigation. It is concluded that LDH may have a diagnostic value in the preclinical stage of malignant lymphoma. Thus, a patient with no apparent cause for elevated serum LDH levels warrants a thorough work-up including abdominal CT scan and even explorative laparotomy.