Thyroid fine needle biopsy (FNB) is the procedure of choice for the management of thyroid nodules. Serious complications after FNB are rare, but there is also an underestimation of complication risk because of record, selection and publication biases. Hypothesis: Apart from the well-documented post-FNB complications, we hypothesized that there are potential complications following FNB, albeit supported by limited evidence in the literature. According to our hypothesis, there may be five distinct expected rare complications: 1) cyst fluid leakage; 2) anaphylactic reaction; 3) pneumothorax; 4) thromboembolism and 5) needle tract seeding of medullary thyroid carcinoma (MTC) or thyroid lymphoma.CONCLUSIONS: Cyst fluid leakage and pneumothorax may be of minimal clinical significance. Needle tract seeding of MTC or thyroid lymphoma may not have significant clinical consequences, if someone considers the easiness and effectiveness of surgical removal of needle tract seeding in cases of differentiated thyroid carcinoma. On the contrary, anaphylactic reaction or thromboembolism may be life-threatening. The performers of thyroid FNB are hereby encouraged to publish these complications, if they ever occur, because awareness of them could render FNB even safer.