Problems and limitations with fine needle aspiration cytology of solitary thyroid nodules

Fine needle aspiration cytology (FNAC) is a widely employed tool in the investigative work-up of patients with single thyroid nodules. Although its advantages are well documented, the limitations and problems in interpretation of FNAC in this condition are not well known. Experience with FNAC in 150 patients with solitary thyroid nodules is presented, highlighting the pitfalls of this technique. There was an inadequate specimen rate of 22.7% which declined with increasing experience. Follicular carcinomas could not be differentiated from follicular adenomas by cytology. Difficulties may arise in the detection of papillary carcinomas due to occult lesions, mixed papillary and follicular carcinomas or due to associated thyroid pathology. False positivity is, however, much rarer and is generally due to cellular adenomatous goitres with marked papillary activity. In view of these cytologic limitations, care must be exercised by the treating physician in interpreting cytological results.