Work-up of thyroid nodule
Most well differentiated cancers present as thyroid nodule. The incidence of malignancy in patients with a solitary nodule and multiple nodules is the same.9–10 In a person presenting with a thyroid nodule it is important to ascer- tain whether malignancy exists. Family history of cancer and exposure to radiation in the past increase the likeli- hood of malignancy. Malignancy is more common at extremes of age, in male sex and in a firm to hard nod- ule. The following three tests are done in all cases of thyroid nodule, namely thyroid function test (TFT), ultra- sonography (USG) and fine needle aspiration cytology (FNAC).
TFT: A low TSH is an indication to perform a thyroid scan as hot or functioning nodules are rarely malignant and an FNAC may be avoided.
USG: Can characterize the nodule and differentiate solid from cystic swelling. Hypoechogenecity, irregular margins, presence of punctate calcification, large size and absence of halo are some indicators of malignancy. FNAC can be targeted.
FNAC: It has a high diagnostic value with a low false positive rate.11 It can classify the nodule as malignant, suspicious for malignancy or benign. It has greater accuracy in diagnosing a papillary carcinoma. It cannot distinguish a follicular adenoma from a carcinoma as vascular and capsular invasion needs to be demonstrated to make the diagnosis.