Session: MON 471-496-Thyroid Neoplasia & Case Reports
Poster Board MON-474
Methods: Retrospective analysis of 9372 18F-FDG-PET exams, performed in Nuclear Medicine Department of Portuguese Institute of Oncology, Lisbon, within 2007 and 2012. The inclusion criteria were focal thyroid uptake in patients studied for nonthyroid purpose. Exclusion criteria were diffuse uptake and known thyroid pathology.
Results: Abnormal uptake (diffuse and focal) was identified in 88 cases. Focal uptake, herein meaning incidentaloma, was seen in 58 cases (prevalence of 0,62%). Cytological diagnosis was available in 21 patients corresponding to: papillary thyroid carcinoma (PTC) in 12, nodular hyperplasia in 6, indeterminate follicular lesions in 2 (follicular adenomas confirmed by histology) and lung cancer metastasis in 1.
Based on cytological criteria, the risk of thyroid malignancy was estimated in 57,1% (12/21). Patients were mostly females (female-to-male=5:1) and the majority was in fifth decade (mean of 56,5±15,7 years). The mean value of the maximum standardized uptake value (SUVmax) was 7,5(±5,2), higher than the observed in benign conditions 5,3(±1,8) (p=0,3).
Ten out of 12 patients with cytology compatible with PTC were submitted to surgery. The diagnosis was confirmed in all, classical variant in 7, follicular variant in 3. Three were multifocal; 6 had extrathyroidal extension; 4 angioinvasion. Two presented cervical lymph nodes metastases; 1 had pulmonary metastases. All patients had radioiodine therapy and 2 patients had second surgery due to locorregional recurrence. At the last observation, 3 patients (30%) had persistence or recurrence of disease. Mean follow-up was 32,7 months.
Conclusion: Focal 18F-FDG-PET thyroid incidentalomas have a considerable risk of malignancy, especially for higher SUVmax. Aggressive histological criteria are found in a considerable number of malignant cases. Therefore, thyroid incidentalomas identified by 18F-FDG-PET should be investigated.
Nothing to Disclose: PM, S, PR, TCF, LS, LD, VL, MJB
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