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BACKGROUND
Differentiated thyroid cancers (DTCs), which include papillary thyroid cancer and follicular thyroid cancer, have a predilection for lymph nodal metastasis. The incidence of lymph node (LN) metastasis in DTC has been reported to be between 20% and 50% at presentation and between 5% and 20% during surveillance in the follow-up period. Surgery is the mainstay of treatment in these cancers. Fine-needle aspiration cytology (FNAC) has been the gold standard for diagnosis at presentation as well as during post-treatment cancer surveillance. Inadequate tissue sample necessitates additional needle passes, however, which may add costs and inconvenience for the patient. Studies have shown that the measurement of thyroglobulin (Tg) levels in the FNA fluid improves the diagnostic results of the FNAC. The American Thyroid Association (ATA) recommends that during follow-up, if a positive diagnosis would change the management, LNs that are suspicious on the ultrasound and are ≥8–10 mm in diameter should undergo FNAC with Tg washout (strong recommendation, low-quality evidence) (Thyroid. 2016;26:1-133).
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BEST PRACTICE
The literature supports the use of Tg washout as an adjunct to FNAC as it improves diagnostic accuracy. The commonly used cutoff value of Tg is 1 ng/mL, according to the ATA guidelines. Tg washout is particularly helpful in cancer surveillance during the follow-up period, especially in suspicious LNs with lower tissue yield or cytologic and discordant ultrasound findings. However, for LNs with highly suspicious ultrasound features of malignancy, FNAC alone suffices for the diagnosis.