From the Guidelines
The risk of a thyroid nodule becoming cancerous after a benign biopsy is quite low, approximately 1-3% over 5 years, as supported by the most recent study 1. Most thyroid nodules that have been classified as benign through fine needle aspiration (FNA) biopsy remain benign. However, follow-up monitoring is still recommended, typically with an ultrasound examination 12-24 months after the initial benign biopsy. For nodules that show no growth or suspicious changes, less frequent monitoring may be appropriate. If the nodule grows significantly (usually defined as more than 20% increase in at least two dimensions) or develops suspicious ultrasound features, a repeat biopsy should be performed. This low malignancy risk is reassuring, but ongoing surveillance is important because initial biopsies can occasionally miss cancerous cells due to sampling error. Certain nodule characteristics may slightly increase the risk of malignancy despite a benign biopsy, including larger size (>4cm), solid composition, irregular margins, microcalcifications, or a family history of thyroid cancer, as noted in previous studies 1. Patients should maintain regular follow-up with their healthcare provider and report any symptoms such as difficulty swallowing, voice changes, or neck discomfort. The management of thyroid nodules is guided by various clinical, radiological, and treatment guidelines, including the Thyroid Imaging Reporting And Data Systems (TIRADSs) and the American Thyroid Association guidelines, which provide recommendations for the management of thyroid nodules and cancer 1. It is essential to consider the complexity in the interpretation and application of multiple guidelines for thyroid nodules, particularly for "small" lesions, and the need for coordinated recommendations 1.
From the Research
Likelihood of Thyroid Nodules Becoming Cancerous
- The likelihood of thyroid nodules becoming cancerous after a benign biopsy is relatively low, with one study finding that only 9 patients (1.2%) had pathology-proven malignancy after a mean follow-up of 3.5 years 2.
- Another study found that the risk of malignancy associated with any cytologic diagnosis was not significantly different when multiple nodules were biopsied, but performing biopsy in 3 nodules detected all carcinomas in the series 3.
- The clinical importance of adequate evaluation of thyroid nodules is highlighted, with a focus on risk assessment for thyroid cancer based on clinical and ultrasound features to guide the need for biopsy 4.
- Ultrasonography (US) is increasingly being employed in the diagnosis and management of patients with thyroid nodules and thyroid cancer, with US characteristics imparting a suspicious appearance on thyroid nodules and cervical lymph nodes 5.
Factors Influencing the Likelihood of Cancer
- The size of the nodule is a factor, with one study finding that 28.8% of nodules decreased in size, 19.4% increased in size by less than 50%, and 12.1% increased in size by more than 50% 2.
- The number of nodules biopsied is also a factor, with performing biopsy in 3 nodules detecting all carcinomas in one series 3.
- The use of minimally invasive therapies, such as percutaneous ethanol injection (PEI) and laser photocoagulation (LP), has been proposed as an alternative to surgery, but the risk to benefit ratio of these treatments is currently unknown 6.
Diagnostic Evaluation and Management
- Recent clinical guidelines advocate a more conservative approach in the evaluation of thyroid nodules based on risk assessment for thyroid cancer 4.
- The use of ultrasound and fine-needle aspiration is recommended for the diagnosis and management of thyroid nodules and thyroid cancer 5.
- A combined assessment including the initial ultrasound risk stratification or other ancillary testing (molecular markers, second opinion on thyroid cytology) can further clarify the risk of thyroid cancer and the management strategies 4.