Abstract
We report hyperamylasemia, macroamylasemia, and a markedly increased amylase clearance/creatinine clearance ratio in a patient with renal cell carcinoma. Serum amylase activity was characterized as macroamylase by gel exclusion chromatography. Electrophoretic separation revealed an atypical band of amylase, migrating anodal to the S2 control fraction. Electrophoresis of urine revealed the presence of both S1 and S2 fractions, but not the atypical band found in serum. Quantification of the salivary- and pancreatic-type amylase fractions showed amylase in urine to be 100% salivary. Immunofixation disclosed the macroamylase to consist of an immune complex between amylase and IgA-lambda antibody. Binding-capacity studies showed that the serum immunoglobulin was present in excess and could bind 46% and 49% additional S-type amylase activity derived from saliva and the patient's urine, respectively. The amylase clearance/creatinine clearance ratio was markedly supranormal (0.134), unexpected in a patient with macroamylasemia. A biopsy specimen of the renal cell tumor was found to contain significant salivary-type amylase activity. These results suggest production of amylase by tumor tissue in the renal carcinoma and secretion of S-type amylase into the patient's urine. Evidently, macroamylase should be confirmed by gel exclusion chromatography.
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