Endocrine Abstracts

Introduction: Incidental focal uptake in the thyroid gland is detected in 1%–2% of 18FDG-PET examinations. FNA is recommended due to an increased risk of malignancy (25–50%), but these figures are extracted from the studied cases (about a half). Moreover there is controversy about the maximum standardized uptake value (Suv_max) ability to discriminate between benign or malignant nodules.

Methods: We retrospectively reviewed 4207 FDG-PET scans performed for non-thyroidal reasons from January 2013 to October 2014 at our institution. Patients with focal thyroid uptake were assessed for age, sex, underlying conditions, Suv_max, TSH, Ultrasound, FNA cytology and pathological findings.

Results: 65 cases (1.54% of PETs) showed focal thyroid uptake, 41 (63%) females, median age (SD) 70 (12) years. Median (SD) SUV_max was 7.4 (6), [1.4–32]. In global 49 patients (75.4%) were found to have cancer, most common lung cancer and lymphoma, and currently 19 patients (29.2%) have died. Ultrasound was performed in 36 patients (55.4%): single nodule 16, multinodular 19, normal 1; mean nodular size 16.6 (9.6) mm; in 9 cases the nodule was suspictious. Twenty-five cases (38.5%) underwent FNA. Bethesda score was I: 6 (24%); II: 10 (40%); III: 1 (4%); IV: 3 (12%); V: 1 (4%); VI: 4 (16%). Seven patients were operated on, 5 were thyroid cancer (papillary 4, anaplasic 1). Higher SUV_max values prompted FNA exam (P 0.01), however any relation was found between SUV_max and cytology (P 0.44) nor nodular size (P 0.07). There was a direct correlation between TSH levels and SUV_max (P<0.001), but disappeared when analizing euthyroidal patients (TSH 0.5–4.5, n 53) P 0.9.

Conclusions: We report similar frequencies and clinical workup of thyroid PEToma compared to previous series. Few cases underwent thyroidectomy, however thyroid cancer was a frequent histological finding. SUV_max could not determine risk of malignancy.