The significance of FNAC in diagnosing differentiated thyroid cancer and the discrepancy between theory and practice - a multi-centre study.

Introduction:  After non-invasive diagnostic modalities high risk thyroid nodules are investigated with fine needle aspiration cytology in order to find the right surgical strategy for suspected malignancies. Despite the clear recommendation by the European and the American associations (ETA, ATA) its clinical value is doubted and its importance in clinical practice not fully clarified.

Methods:  A multicentric study of 119 patients with differentiated thyroid cancer operated on in 24 surgical departments was conducted. The aim was not only to evaluate the use of FNAC as a diagnostic tool, but also to investigate its diagnostic validity and compare it with that of other, non-invasive diagnostic methods.

Results:  FNAC was used only in 25 % of malignant thyroid nodules. In these patients sensitivity of FNAC was 60 %. In 40 % with preoperative FNAC, the result had an impact on the surgical approach. 17 % underwent surgery only because of the FNAC result, and 23 % underwent a planned surgical resection with total thyroidectomy and lymphadenectomy on account of the FNAC result. In comparison to non-invasive diagnostics (ultrasonography in conjunction with scintigraphy with Na99mTcO4) FNAC reached the same sensitivity.

Discussion:  The results of our study reveal a limited application of preoperative FNAC in diagnosing thyroid nodules as well as a limited conclusiveness in our study population if not performed according to standards. In order to increase the benefits of this diagnostic modality, it seems to be important to perform FNAC according to the guidelines and in a standardized manner. FNAC should always be conducted in combination with ultrasonography. An experienced cytopathologist should be consulted and the Bethesda classification system should be established.