Personalized nuclear imaging protocol in cases with nodular goiter and parathyroid adenoma.

A 62 years old woman was diagnosed with multinodular toxic goiter and primary hyperparathyroidism/left parathyroid adenoma by hormonal assessment, ultrasound and nuclear thyroid/parathyroid scans. Cervical ultrasound illustrated a multinodular aspect of the thyroid with solid nodules and cystic-component nodules; the larger one represented a multinodular complex with necrosis areas in the left thyroid lobe, ACR TI-RADS score 4 (moderately suspicious). Functional nuclear imaging was performed for accurate differential diagnosis between thyroid vs. parathyroid localization, between cold vs. hot nodules, and eventually, for guiding the choice of a subsequent Fine-Needle Aspiration Biopsy (FNAB). Scans described an early intense 99mTc-sestaMIBI uptake with no 99mTc-pertechnetate uptake in the left thyroid lobe larger nodule. Due to the suspicion of malignancy for this nodule, we performed an additional scan (1 hour before the classical 2 hours parathyroid delayed scan). The intense uptake persists in both delayed scans suggesting no malignant phenotype and which was confirmed after surgery by benign histology. In conclusion, using a 99mTc-sestaMIBI personalized protocol, related to the radiotracer cellular uptake mechanisms: 1 hour scan (supplementary image, corresponding to the maximum uptake pattern of 99mTc-sestaMIBI for cancer cells) and 2 hours scan (for parathyroid washout evaluation) may avoid unnecessary extensive thyroid surgery.

99mTc MIBI THYMIC SCINTIGRAPHY IN DIAGNOSIS AND THERAPEUTIC DECISION MAKING: WHAT IS BEHIND THE IMAGE?

CONTEXT: Despite CT being generally used in thymic pathology, in the case of regions with the same tissue density, only functional radioisotopic imaging can hint towards malignity. OBJECTIVES: To assess the usefulness of 99mTc MIBI scintigraphy for diagnosis and treatment planning in thymoma, in relation with the radiotracer uptake mechanism. PATIENTS AND METHODS: 99mTc MIBI thymic scans for 19 patients diagnosed with thymic disorders were assessed using tumor uptake ratio (UR). Specimens of thymectomies were examined and cytological assessments were correlated with the UR. RESULTS: The UR of all surgical patients was higher than 1.2, with a 1.5 cutoff between lymphoid hyperplasia and thymoma. The UR values were correlated with the histopathologic diagnosis (Pearson correlation 0.91, significant at p<0.01). The highest UR was 3.24, found in the case of an AB thymoma where the rate lymphocytes/epithelial cells (L/E) was 1.6. In B1 thymoma UR was 1.14 and L/E was 2.46. CONCLUSION: Phenotype differences between thymoma types correlate with 99mTc MIBI cellular uptake: lower rate L/E corresponds to higher UR, higher malignity potential and invasiveness. A thymic 99mTc MIBI UR higher than 1.5, corresponding to a CT tumoral image, is suggestive for a thymoma, requiring surgical treatment first.