Retrospective Analysis of PSMA PET/CT Thyroid Incidental Uptake in Adults: Incidence, Diagnosis and Treatment/outcome in a Tertiary Cancer Referral Center and an Academic Hospital

Purpose A prostate-specific membrane antigen (PSMA) thyroid incidentaloma (PTI) is an unexpected, PSMA-avid thyroid lesion, newly detected during the investigation of an unrelated condition using PSMA PET/CT. The aim of this study is to examine the incidence and clinical significance of PTI and the associated management strategies since the implementation of the PSMA PET/CT scan. Methods This study involves a retrospective cohort study of 61 PTI cases depicted on PSMA PET/CT scans performed between January 2016 and July 2021, almost exclusively for (re)staging prostate cancer. The medical records of the included cases were retrospectively reviewed and data of the PSMA PET/CT scans, primary malignancy, thyroid diagnostics, treatment and follow-up were collected. Results PTI was reported in 1.1% of the oncologic PSMA PET/CT scans included in this study. Two PTI cases had a histologically proven thyroid cancer, one a benign thyroid lesion and one a metastasis of a renal cell carcinoma. In none of the cases in whom any form of further thyroid work-up was withheld, the PTI became clinically relevant during follow-up (median 1.8 years (1.1-3.3)). Six patients (10%) died due to their primary cancer.Conclusion The incidence of thyroid incidentalomas on PSMA PET/CT was low (1.1%) in this large, two-center experience. Less than half of the PTI cases were analyzed and the risk of malignancy, despite being low, was not negligible. The clinical outcome was good using a standard diagnostic work-up for PTI, while the prognosis of the patient was determined by the primary malignancy. The consideration to analyze and treat PTI cases should be part of the shared decision making in cancer patients.

Thyroid incidentaloma: next to be neglected or investigated?

In modern clinical practice, thyroid incidentaloma is an unpalpated node in the thyroid gland, which is detected accidentally by technical means of imaging when examining a patient for other, non-thyroid diseases. Its dimensions are limited to 10 mm, the limit above which it can already be palpated by a qualified professional. In the author’s view, such a definition narrows the concept of incidentaloma, primarily from a nosological point of view. Under the definition of the node can be micro- or macrofollicular nodular goiter, tumor, benign (adenoma) or malignant (carcinoma), the focus of thyroiditis, cyst, inflammatory focus (infiltrate, abscess), calcifications. When enumerating the me­thods of detection by incidental, the palpation method is excluded and the nodes in the thyroid gland detected with its help are not only up to 10 mm in size but also larger, which should also be called incidental. The same can be said about the nodes that are accidentally found on the neck during operations for diseases of the trachea, cervical esophagus, salivary glands. Speaking of incidentalomas, which are detected at autopsy, it should be noted that some of them are larger than 10 mm. All these positions do not fit into the definition of thyroid incidentaloma only as an unpalpated node in the thyroid gland up to 10 mm, which is determined by instrumental imaging methods. Therefore, the concept of thyroid incidentaloma is broader and more capacious than formulated by its modern definition. Incidental thyroid disease should be considered any additional formation in it, regardless of its size, detected by any non-target method of research. Unpalpated and, as a rule, clinically “dumb” nodes up to 10 mm, determined by instrumental methods, can be considered as one of the subspecies of the incidentaloma. The frequency of their detection has increased sharply in recent years, some are malignant neoplasms with an unpredictable course, tactical approaches to them have not been finalized.

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.

Epidemiologic, Clinical, Ultrasonographic, and Cytological Features of Thyroid Nodules in Predicting Malignancy Risk: A Retrospective Study of 442 French Afro-Caribbean Patients

Objective. To evaluate epidemiologic, clinical, cytological, and ultrasonographic features of thyroid nodules in a sample French Afro-Caribbean population to determine if the standard criteria for predicting malignancy risk are applicable to this specific ethnic population. Methods and Design. This retrospectively designed study consisted of 442 patients who had consulted with the Endocrinology Department in Martinique (French overseas department) between 2007 and 2011. Of the 442 patients, 641 ultrasound-guided fine-needle aspirations (US-FNA) were performed by two experienced endocrinologists, and 212 patients underwent surgery. The geographical situation, age, gender of the patient, clinical and ultrasonographic features, TSH level, and US-FNA results were considered and cross-referenced with their pathology results. Results. The overall malignancy rate on final histopathology was 9% (women only), 80% of which were papillary cancer, and 20% were follicular cancer. Occult micropapillary carcinoma represented 35% of the papillary cancer. There was no significant difference in age, nodule localization, number of nodules, or thyroid function test between benign and malignant nodules. Contrary to the literature, we found only 12% incidentaloma in our series, while more than half of the nodules were discovered on palpation or as a clinical symptom. Hypoechogenicity in solid pattern nodules and nodules between 2 and 3 cm in size revealed a high diagnostic value in detecting malignancy. The corresponding rate of malignancy on Bethesda system histopathologic examination was as follows: 0% in undiagnosed (I), 0% benign (II) (micropapillary), 5% (FLUS)/atypia (III), 9% follicular neoplasm (IV), 33% suspected malignancy (V), and no malignant cytology (VI). These results show a different Bethesda system predictive value for this French Afro-Caribbean population. Conclusion. Studies evaluating ethnic cancer disparities among patients with thyroid cancer are limited and do not specifically focus on the French Afro-Caribbean population. Despite rare thyroid incidentaloma, 35% of the papillary cancer cases were micropapillary carcinoma, and the incidence and standardized mortality rate in Martinique are lower than in metropolitan France. The malignant risk distribution of thyroid FNA Bethesda classification in this sample population differs from the standard risk, and it is necessary to take that into account in the decision to operate by associating it with echographic malignancy criteria.