From the Guidelines
Fine needle aspiration (FNA) is not absolutely required for a 4.5 cm thyroid nodule without suspicious sonographic features, as decisions to aspirate larger nodules should be guided by lesion size and sonographic appearance. According to the ESMO clinical practice guidelines for diagnosis, treatment, and follow-up of thyroid cancer 1, the diagnostic work-up of differentiated thyroid cancers (DTCs) comprises pre- and postoperative pathological and molecular assessments. While FNA for cytology is not required for nodules measuring 1 cm, decisions to aspirate larger nodules should consider both the size of the nodule and its sonographic appearance.
Some key points to consider in the evaluation of thyroid nodules include:
- The size of the nodule, with larger nodules carrying a higher risk of malignancy
- The sonographic appearance of the nodule, with certain features being more suspicious for cancer
- The use of FNA to obtain cytology samples for evaluation
- The classification of cytology findings into diagnostic categories associated with different risks of malignancy
It's also important to note that while FNA can identify most malignant thyroid tumors, there are exceptions, such as follicular thyroid cancers (FTCs) and the newly defined ‘non-invasive follicular thyroid neoplasm with papillary-like nuclear features’ (NIFTP), which are usually classified as indeterminate 1. Therefore, the decision to perform FNA on a 4.5 cm thyroid nodule should be individualized, taking into account the specific characteristics of the nodule and the patient's overall clinical context.
From the Research
Thyroid Nodule Assessment
The assessment of thyroid nodules involves several components, including clinical history and examination, serum thyroid stimulating hormone (TSH) measurement, ultrasound, and fine-needle aspiration (FNA) if indicated 2.
Fine-Needle Aspiration (FNA) Recommendations
FNA may be performed for nodules ≥ 1.0 cm depending on clinical and sonographic risk factors for thyroid cancer 2. However, for a 4.5 cm thyroid nodule, the recommendation for FNA is not explicitly stated in the provided studies.
Ultrasound Features and Risk of Malignancy
Several ultrasound features have been associated with an increased risk of malignancy, including:
- Microcalcifications
- Irregular margins
- Taller than wide shape
- Absence of elasticity These features can help identify nodules with an increased risk for malignancy, but no single feature is sufficiently reliable in isolation to diagnose malignancy 3, 4.
Risk Stratification Systems
Ultrasound risk stratification systems (RSSs) have been developed to reduce the number of unnecessary FNA biopsies, but they may prompt inappropriate FNA in autonomously functioning thyroid nodules (AFTNs) 5.
Multimodality Ultrasound
Multimodality ultrasound utilizing microvascular flow imaging and shear wave elastography may improve the differentiation of benign and malignant thyroid nodules and potentially reduce the risk of unnecessary biopsy of benign thyroid nodules 6.
Decision to Perform FNA
The decision to perform FNA on a 4.5 cm thyroid nodule should be based on a combination of clinical and sonographic risk factors, as well as the presence of suspicious ultrasound features. However, the provided studies do not offer a clear recommendation for FNA in this specific case.