PREOPERATIVE DIAGNOSTIC-TESTS FOR OPERABLE THYROID-DISEASE

Although the availability and acceptance of fine-needle aspiration bio psy (FNAB) of thyroid nodules has increased, many physicians still use thyroid scintigraphy for distinguishing benign from malignant lesions . We evaluated these diagnostic: tests in 350 patients who had thyroid surgery in our institution between 1977 and 1990. Histologic confirma tion of FNAB was obtained in 265 patients. In the group of patients ha ving surgery, 247 thyroid scintigraphies were performed. Our patients were divided into two groups (1977-1986 and 1986-1990). The first grou p comprised 173 patients with 173 FNABs and 126 scintigrams. The secon d group consisted of 177 patients having 92 FNABs and 121 scintigrams. Results of scintigrams were analyzed in the second group only. In 5 o ut of 120 cases where the FNAB result was ''benign or probably benign' ' the lesion appeared to be malignant postoperatively. If the FNAB res ult was ''malignant or probably malignant'' (n = 83) the pathology rep ort confirmed a malignancy in 68 cases (81.9%). In 56 instances of all 265 FNABs the cytology report was not conclusive (''uncertain''); in 21.4% of these cases a malignancy was found postoperatively. An FNAB-r esult ''(probably) malignant'' had a positive predictive value of 0.81 9 while the negative predictive value of a result ''(probably) benign' ' is 0.950. An ''uncertain'' result does not take away our concern so this result should have the same consequences as those of a result ''( probably) malignant''. In that case, FNAB-sensitivity is 93.0% and spe cificity 66.1%. Eighty-five of the last 116 scintigraphies showed a so litary node. Eleven of these nodes were hot while 74 were cold. In 2 o ut of 11 hot nodules cancer was diagnosed (18.2%). Twenty-six of the c old nodules contained a malignancy (35%). Evaluation of 116 Te-99m sci ntigrams yielded a positive predictive value of finding a malignancy i n the thyroid if the scan showed a solitary cold nodule of 0.351. If a cold nodule is supposed to be an indicator of malignancy this test ha s a sensitivity of 72.2% and a specificity of 43.5%. The accuracy is a s low as 52.1%. Our data indicate that the accuracy rate of nuclear im aging techniques in diagnosing thyroid nodules is low. There is no pla ce for routine scintigraphy in preoperative diagnosis of a thyroid les ion. Although observer dependency exists with FNAB, the overall accura cy of this test is high, while this low-cost test is easy to perform a nd increasingly available. It enables cancer detection in a cost-effec tive manner. We recommend surgery for a clinically suspicious lesion a nd if the FNAB result is uncertain, probably malignant, or malignant. We advocate direct total thyroidectomy if the FNAB result is malignant , peroperative frozen section after hemithyroidectomy if the FNAB resu lt was probably malignant or in a clinically suspicious lesion regardl ess of the FNAB result (unless malignant). A diagnostic hemithyroidect omy only, without frozen section, is performed if the FNAB result was uncertain.