BIOCHEMICAL-ANALYSIS OF THYROID CYST FLUID OBTAINED BY FINE-NEEDLE ASPIRATION

Despite the relatively ready availability of thyroid cyst fluid specim ens, little has been published on their biochemical composition. We me asured the concentrations of 18 analytes in thyroid cyst fluid specime ns from benign (n=17) and malignant (n=3) lesions and in homogenates o f normal thyroid tissue (n=5). The concentrations of an additional fiv e analytes were measured in selected cyst fluid specimens only. Compar ed with normal human serum specimens, we found that in thyroid cyst fl uid specimens the activities of acid phosphatase, aspartate aminotrans ferase, amylase, and lactate dehydrogenase, and the concentrations of iron and total bilirubin were highly increased. The concentration of g lucose was low. The gross appearance of the fluids and the presence of certain analytes were consistent with a hemorrhagic origin of most of the benign and malignant cyst fluid specimens. Other biochemical mark ers, however, indicated colloidlike features and/or an admixture of th yroid tissue components to the cyst fluid. Although we have limited da ta for cyst fluid specimens from malignant thyroid lesions, we found n o evidence that the results of any of the common biochemical tests wou ld distinguish benign from malignant lesions.