Hürthle Cells on Fine-Needle Aspiration Cytology Are Important for Risk Assessment of Focally PET/CT FDG Avid Thyroid Nodules

Consensus statement on the management of incidentally discovered FDG avid thyroid nodules in patients being investigated for other cancers

With the widespread use of 18F-fluorodeoxyglucose positron emission tomography (FDG PET/CT) in the investigation and staging of cancers, incidental discovery of FDG-avid thyroid nodules is becoming increasingly common, with a reported incidence in the range 1%-4% of FDG PET/CT scans. The risk of malignancy in an incidentally discovered FDG avid thyroid nodule is not clear due to selection bias in reported retrospective series but is likely to be less than 15%. Even in cases where the nodule is found to be malignant, the majority will be differentiated thyroid cancers with an excellent prognosis even without treatment. If, due to index cancer diagnosis, age and co-morbidities, it is unlikely that the patient will survive 5 years, further investigation of an incidental FDG avid thyroid nodule is unlikely to be warranted. We provide a consensus statement on the circumstances in which further investigation of FDG avid thyroid nodules with ultrasound and fine needle aspiration might be appropriate.

The Impact of the 2022 WHO Classification of Thyroid Neoplasms on Everyday Practice of Cytopathology

This review outlines how the alterations in the 5th edition of the WHO Classification of Endocrine and Neuroendocrine Tumors of the thyroid gland are likely to impact thyroid cytopathology. It is important to note that WHO subclassifies thyroid tumors into several new categories based on increased comprehension of the cell of origin, pathologic features (including cytopathology), molecular classification, and biological behavior. The 3rd edition of the Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) will debut in the near future and will include changes in diagnostic category designations. The changes in the 5th edition of the WHO will in some instances subtly, and in other instances significantly, impact the cytological diagnoses. Moreover, these changes will also affect other thyroid FNA classification schemes used internationally for classifying thyroid FNA specimens.

Systematic review and meta-analysis of the diagnostic value of radionuclide imaging for thyroid nodules

BACKGROUND

There are many studies on diagnostic imaging of thyroid nodules, among which radionuclide scanning imaging has been proven to be very effective in identifying malignant lesions of thyroid nodules and is now widely used in the clinical detection of thyroid nodules.

METHODS

Studies on radionuclide imaging in the diagnosis of thyroid nodules were searched in multiple Chinese and English databases, including PubMed, Web of Science, Embase, and The Cochrane Library as of July 1, 2021. The search terms included "clinical experiment", "thyroid nodule", "radionuclide imaging", "thyroid mass", "thyroid masses", "postoperative pathology", and "histopathology". The basic information and evaluation indicators in the literature were screened and extracted. Subsequently, meta-analysis was performed using RevMan 5.3 and Stata 13 software provided by the Cochrane system. In addition, forest plots and summary receiver operating characteristic (SROC) curves were drawn.

RESULTS

Seven randomized controlled trails (RCTs) were included in this study. The radionuclide imaging of thyroid nodule showed the area under SROC curve of 0.38. The combined diagnostic sensitivity and specificity were 0.66 [95% confidence interval (CI): 0.46, 0.89] and 0.36 (95% CI: 0.21, 0.59), respectively. The combined positive likelihood ratio (LR) and negative LR were 0.66 (95% CI: 0.53, 0.87) and 0.67 (95% CI: 0.43, 0.95), respectively. In addition, the combined diagnostic odds ratio (OR) was 4.45 (95% CI: 0.25, 10.57).

DISCUSSION

In this study, meta-analysis was used to confirm the application value of radionuclide imaging in the diagnosis of thyroid nodules. In the future, the value of radionuclide imaging in the diagnosis of thyroid nodules should be compared with other imaging detection methods.

The dilemma of 18F-FDG PET/CT thyroid incidentaloma: what we should expect from FNA. A systematic review and meta-analysis

PURPOSE

¹⁸F-FDG thyroid incidentaloma (TI) occurs in ~2% of PET/CT examinations with a cancer prevalence of up to 35-40%. Guidelines recommend fine-needle aspiration cytology (FNA) if a focal ¹⁸F-FDG TI corresponds to a sonographic nodule >1 cm. The aim of this systematic review and meta-analysis was to provide evidence-based data on the diagnostic distribution of ¹⁸F-FDG TIs in the six Bethesda systems for reporting thyroid cytopathology (BETHESDA) subcategories.

METHODS

Original studies reporting ¹⁸F-FDG TIs and cytologically classified according to BETHESDA were included. Six separate meta-analyses were performed to obtain the pooled prevalence (95% confidence interval, 95% CI) of ¹⁸F-FDG TIs in the six BETHESDA subcategories.

RESULTS

Fifteen studies were finally included. Nine studies were from Asian/Eastern and six from Western countries. FNA data according to BETHESDA was available in 2304 cases. The pooled prevalence of ¹⁸F-FDG TIs according to BETHESDA was BETHESDA I 10% (6-14), BETHESDA II 45% (37-53), BETHESDA III 8% (3-13), BETHESDA IV 8% (5-12), BETHESDA V 6% (4-9), BETHESDA VI 19% (13-25). A significantly different prevalence was found in the BETHESDA IV between Asian/Eastern (2%) and Western (19%) studies.

CONCLUSION

Two-thirds of focal ¹⁸F-FDG TIs undergoing FNA have either malignant (BETHESDA VI) or benign (BETHESDA II) cytology while a minority will have indeterminate (BETHESDA III or IV) FNA results. Significant differences between Asian/Eastern and Western studies are also present in the prevalence of indeterminate FNA results.