From the Guidelines
The gold standard for diagnosing thyroid cancer is a fine needle aspiration (FNA) biopsy followed by histopathological examination, as it provides high sensitivity and specificity for detecting malignant thyroid nodules. This procedure involves inserting a thin needle into the thyroid nodule to extract cells, which are then examined under a microscope by a pathologist 1. FNA biopsy is typically performed on thyroid nodules that are suspicious based on ultrasound characteristics, size (usually greater than 1 cm), or growth pattern. The procedure is minimally invasive, can be done in an outpatient setting, and usually takes only a few minutes to complete. Local anesthesia may be used to minimize discomfort.
The extracted cells are analyzed using cytological criteria such as the Bethesda System for Reporting Thyroid Cytopathology, which categorizes findings into six diagnostic categories ranging from benign to malignant 1. While FNA biopsy has high sensitivity and specificity, in some cases with indeterminate results, additional molecular testing of the biopsy sample or a surgical biopsy may be necessary for definitive diagnosis. The accuracy of FNA diagnosis is enhanced when performed under ultrasound guidance, which helps ensure the needle is placed precisely within the suspicious area of the thyroid.
Some key points to consider when performing FNA biopsy include:
- Using ultrasound guidance to ensure accurate needle placement
- Considering molecular diagnostic testing to detect individual mutations or pattern recognition approaches using molecular classifiers for indeterminate FNA samples 1
- Evaluating FNA samples using the Bethesda System for Reporting Thyroid Cytopathology
- Performing FNA biopsy on thyroid nodules that are suspicious based on ultrasound characteristics, size, or growth pattern.
It's worth noting that other diagnostic methods, such as measurement of serum calcitonin, may be useful in specific cases, such as medullary thyroid cancer, but FNA biopsy remains the gold standard for diagnosing thyroid cancer in general 1.
From the Research
Diagnosing Thyroid Cancer
The gold standard for diagnosing thyroid cancer involves fine-needle aspiration biopsy (FNAB) [(2,3,4,5,6)]. This method has proven to be accurate for the detection of thyroid cancer.
Fine-Needle Aspiration Biopsy (FNAB)
- FNAB is an accurate, slightly invasive, and safe method for the preoperative diagnosis of thyroid nodules 3.
- The diagnostic accuracy of FNAB can be enhanced with ultrasound guidance 3.
- Ultrasound-guided FNAB allows for a more precise and adequate sampling of thyroid nodular lesions and is associated with a lower rate of false-negatives 3.
Molecular Testing
- Molecular testing of cytology specimens from thyroid nodules has the potential to play a major role in the evaluation of indeterminate thyroid lesions 5.
- Several commercially available tests, including the Afirma Gene Expression Classifier, ThyGenX, and ThyroSeq, can be used to assess the risk of malignancy 5.
- These tests have excellent negative predictive value (NPV) and positive predictive value, allowing them to be used as "rule out" and "rule in" tests 5.
Indeterminate Cytology Diagnoses
- Indeterminate cytology diagnoses remain a diagnostic challenge 5.
- Integration of new molecular markers is opening new perspectives in order to increase the diagnostic precision of thyroid nodules with an indeterminate cytology 6.
- Repeat aspiration is often successful and should be the standard approach to such nodules, given their risk of malignancy 2.