Nuclear medicine imaging modalities to detect incidentalomas and their impact on patient management: a systematic review

Meta-Analysis on the Prevalence and Significance of Incidental Findings in the Thyroid Gland Using Other PET Radiopharmaceuticals Beyond [18F]FDG

Background: Meta-analyses on the prevalence and significance of thyroid incidentalomas at PET (TIP) are available only about [18F]FDG. Focal TIP at [18F]FDG PET is not rare and may be malignant lesions in about one-third of cases. The aim of this study is to perform a meta-analysis on the prevalence and clinical significance of TIP using other PET radiotracers beyond [18F]FDG. Methods: A comprehensive literature search of studies about TIP was carried out using four different databases, screened until 31 December 2024. Only original articles about TIP using radiopharmaceuticals other than [18F]FDG were selected. A proportion meta-analysis on the prevalence and clinical significance of TIP was carried out on a patient-based analysis using a random-effects model. Results: 21 studies (29,409 patients) were included in the meta-analysis. PET was performed using radiolabeled somatostatin analogues (SSA) [n = 5], choline [n = 6], prostate-specific membrane antigen (PSMA) [n = 7], or fibroblast activation protein inhibitors (FAPI) [n = 3]. The uptake pattern of TIP was described as focal, diffuse, or mixed/heterogeneous. The pooled prevalence of TIP was 5.6% for SSA-PET, 6.1% for choline-PET, 4.2% for PSMA-PET, and 3.6% for FAPI-PET. The final diagnosis of TIP with a diffuse pattern was a benign condition or represented a physiological uptake. Conversely, TIP with focal or mixed/heterogeneous pattern may represent a benign condition in most cases, but even a malignant lesion in 6-10% of cases. Conclusions: As for [18F]FDG, TIP using other radiopharmaceuticals is not rare. Most of them are benign, but those with focal or heterogeneous uptake patterns may represent a malignant lesion in some cases (even if the risk of malignancy is lower compared to [18F]FDG PET), thus requiring further evaluation. Further studies are warranted to better clarify the clinical impact of TIP detection.

Diagnostic Characteristics and Clinical Relevance of Incidental Hypermetabolic Breast Lesions Detected on 18F-FDG PET-CT: A Retrospective Evaluation

RATIONALE AND OBJECTIVES

The study aimed to evaluate demographic and radiological characteristics of breast incidentalomas found on 18-fluorodeoxyglucose Positron Emission Tomography-Computed Tomography (18F-FDG PET-CT) performed for extramammary indications.

MATERIALS AND METHODS

A total of 12633 18F-FDG PET-CT scans performed between January 1, 2018 and January 1, 2024, were retrospectively reviewed. Breast incidentalomas that had undergone breast imaging, tissue diagnosis, or at least 2-year radiological follow-up were included. Demographic data and lesion size were recorded. Maximum and average standardized uptake values (SUVmax-SUVavg) and SUV corrected for lean body mass (SUL) were calculated using region of interest (ROI).

RESULTS

The inclusion criteria were met in 101 lesions (81 benign and 20 malignant). The most common benign lesion was fibroadenoma (n = 21), followed by stable lesions during follow-up (n = 18) and benign breast parenchyma (n = 11). The most common malignant lesion was invasive ductal carcinoma (n = 11). The diagnostic characteristics of SUVmax≥ 3, SULmax≥ 2, SUVavg≥ 0.735, SULavg≥ 0.48, and BI-RADS≥ 4 were 75%, 70%, 75%, 70% and 100% for sensitivity, 69%, 69%, 62%, 62% and 67% for specificity, and 69.3%, 68.3%, 62.4%, 61.4% and 73.3% for accuracy, respectively. The highest negative predictive values (NPV) were obtained with BI-RADS and SUVmax (100% and 92%, respectively). No significant difference in malignancy rate was observed for the lesion size and age of the patients (p > 0.05).

CONCLUSION

There is a risk of detecting malignancy in incidental lesions showing 18F-FDG uptake. Radiological workup must be done, but SUVmax, with a high NPV value, can be used in conjunction with BI-RADS assessment for appropriate patient selection and effective management of resources.

Ectopic Mediastinal Thyroid: A Crossroad Between a Multi-Layered Endocrine Perspective and a Contemporary Approach in Thoracic Surgery

An ectopic thyroid (ET) involves numerous scenarios of detection and outcomes, while its current management is not standardised. A mediastinal ET (MET) represents a low index of suspicion. In this paper, we introduce a 47-year-old female who was accidentally identified with an MET, and a modern surgical approach was provided. An anterior mediastinal mass of 3.2 cm was found at CT upon a prior COVID-19 infection. Previous to the infection, she experienced non-specific complaints for a few months (intermittent night sweats, facial erythema, chest pressure, and dyspnoea). Also, CT identified a thymus-like mass and a left adrenal incidentaloma of 3 cm. The endocrine panel was normal, and the subject declined further investigations. She was re-admitted 12 months later: the MET had increased +1 cm (+45% volume) and was confirmed at a 99mTc pertechnetate scintigraphy. Noting the symptoms, mediastinal anatomy, and size change, the MET was removed via a minimally invasive trans-cervical approach (eutopic gland preservation) with the help of a Cooper thymectomy retractor (which also allowed for a synchronous thymus mass resection). No post-operatory complications were registered, the thyroid function remained normal, and the mentioned symptoms were remitted. A histological exam confirmed a benign MET and thymus hyperplasia, respectively. To conclude, this case pinpoints important aspects, such as the clinical picture became clear only upon thoracic surgery due to the complete remission of the complaints that initially seemed widely non-specific. The incidental MET finding was associated with a second (adrenal) incidentaloma, a scenario that might not be so rare, following multiple imaging scans amid the COVID-19 era (no common pathogenic traits have been identified so far). The co-presence of a thymus mass represented one more argument for surgery. Minimally invasive cervicotomy associated with eutopic gland conservation and the use of a Cooper thymectomy retractor highlight modern aspects in video-assisted thoracic surgery, which provided an excellent outcome, involving one of the lowest mediastinal thyroids to be removed by this specific procedure. Awareness of such unusual entities helps inform individualised, multidisciplinary decisions for optimum prognoses.

A Real-World Longitudinal Study in Non-Functioning Pituitary Incidentalomas: A PRECES Micro-Adenomas Sub-Analysis

Background. Incidentalomas have an increasing incidence all over the world due to a larger access to imaging assessments, and endocrine incidentalomas make no exception in this matter, including pituitary incidentalomas (PIs). Objective. Our objective was to analyse the dynamic changes amid a second computed tomography (CT) scan after adult patients were initially confirmed with a PI (non-functioning micro-adenoma). Methods. This was a multi-centric, longitudinal, retrospective study in adults (aged between 20 and 70 y) amid real-world data collection. We excluded patients who experienced baseline pituitary hormonal excess or deficiency or those with tumours larger than 1 cm. Results. A total of 117 adults were included (94.02% females) with a mean age of 43.86 ± 11.99 years, followed between 6 and 156 months with a median (M) of 40 months (Q1 Q3: 13.50, 72.00). At the time of PI diagnosis, the transverse diameter had a mean value of 0.53 ± 0.16 cm, the longitudinal mean diameter was 0.41 ± 0.13 cm, and the largest diameter was 0.55 ± 0.16 cm. No PI became functioning during follow-up, neither associated hypopituitarism nor increased >1 cm diameter. A total of 46/117 (39.32%) patients had a larger diameter during follow-up (increase group = IG) versus a non-increase group (non-IG; N = 71, 60.68%) that included the subjects with stationary or decreased diameters. IG had lower initial transverse, longitudinal, and largest diameter versus non-IG: 0.45 ± 0.12 versus 0.57 ± 0.17 (p < 0.0001), 0.36 ± 0.11 versus 0.43 ± 0.13 (p = 0.004), respectively, 0.46 ± 0.12 versus 0.6 ± 0.16 (p < 0.0001). IG versus non-IG had a larger period of surveillance: M (Q1, Q3) of 48 (24, 84) versus 32.5 (12, 72) months (p = 0.045) and showed similar age, pituitary hormone profile, and tumour lateralisation at baseline and displayed a median diameter change of +0.14 cm versus -0.03 cm (p < 0.0001). To conclude, a rather high percent of patients might experience PI diameter increase during a longer period of follow-up, including those with a smaller initial size, while the age at diagnosis does not predict the tumour growth. This might help practitioners with further long-term surveillance protocols.