Thyroid aspiration cytology in Newcastle: a six year cytology/histology correlation study

Fine needle aspiration cytology (FNAC) is a well-established technique for pre-operative investigation of thyroid nodule(s). Thyroid FNAC was introduced in the teaching hospitals of Newcastle upon Tyne in 1981, initially with a small group of clinicians as aspirators. Audit results for 1981-1986 inclusive showed an unsatisfactory rate of 25.3% and prediction of malignancy with a sensitivity of 93.5%. FNAC has become more popular locally for the investigation of thyroid disease and the number of clinicians performing aspirates has increased. The results for recent years have, therefore, been audited.

Medical records were reviewed for 239 patients with a dominant thyroid nodule who had FNAC carried out in the 6 year period 1990-1995 and subsequent partial or complete thyroidectomy.

Histology of thyroid specimens showed 60 follicular adenomas and 34 malignant lesions (including 19 papillary, 10 follicular and 3 medullary carcinomas, one lymphoma and one follicular neoplasm with indeterminate malignant potential). A total of 302 FNAC had been carried out on these 239 patients. On cytological grounds the unsatisfactory sample (AC0 and AC1) rate was 43.1% on initial aspiration which was reduced to 32.2% on repeated aspiration. FNAC predicted neoplasia (AC3, AC4 and AC5) with a sensitivity of 86.8%, a specificity of 67.0%, a negative predictive value of 87.5% and a positive predictive value of 65.5%. Malignancy was predicted by FNAC (AC3, AC4 and AC5) with a sensitivity of 88.9%. A FNAC report of AC5 had a positive predictive value for malignancy of 100%.

FNAC is an invaluable and minimally invasive procedure for the pre-operative assessment of patients with a dominant thyroid nodule. It is, however, important that the number of aspirators and cytopathologists be kept small to maintain expertise and also that the results of FNAC be subjected to ongoing audit.