The increasing use of imaging for health screening, cancer staging, treatment monitoring, and non-thyroidal disease evaluation has led to frequent detection of endocrine incidentalomas. Thyroid incidentalomas are among the most common of these findings. With advances in modern molecular oncology, functional imaging has expanded from FDG-PET/CT to non-FDG PET tracers targeting prostate-specific membrane antigen (PSMA), somatostatin receptors (SSTR), choline metabolism, fibroblast activation protein (FAP), and other tumor- or microenvironment-related pathways. Consequently, endocrinologists are increasingly required to interpret and manage incidental thyroid findings detected across diverse imaging platforms..
While most thyroid incidentalomas are benign or clinically indolent, a distinct subset represents clinically relevant malignancies. At the same time, indiscriminate workup can lead to overdiagnosis, overtreatment, patient anxiety, and unnecessary healthcare utilization. Optimal management therefore requires understanding of how prevalence, malignancy risk, prognostic relevance, and imaging predictors vary by specific modality. For instance, while focal FDG uptake is associated with a relatively high malignancy risk, SUVmax thresholds alone lack definitive diagnostic specificity. In CT- or MRI-detected nodules, structural characteristics such as size, suspicious lymphadenopathy, and local invasion are more informative than nonspecific signal or attenuation characteristics. For emerging PET tracers, tracer-specific biology and false-positive mechanisms must be considered before extrapolating FDG-PET-based management strategies.
This lecture will review thyroid incidentalomas detected by conventional structural imaging and emerging functional PET modalities, summarizing current evidence on prevalence, malignancy risk, and imaging features associated with malignancy and prognosis. Ultimately, we propose a practical, patient-centered approach that balances clinically meaningful cancer detection with avoidance of overdiagnosis and overtreatment.