Differential Tumor Biology Between Locoregional and Distant Metastasis in a TENIS Patient with Tyrosine Kinase Inhibitor-Resistant Recurrent Disease: Comparative Evaluation with 18F-FDG, 68Ga-DOTATATE, and 68Ga-PSMA-11 PET/CT

We present themolecular PET/CT imaging profile of an interesting case of differentiated thyroid carcinoma that later transformed into TENIS (thyroglobulin elevation and negative iodine scintigraphy) with tyrosine kinase inhibitor-resistant recurrent, aggressive disease. The patient was evaluated to assess somatostatin receptor 2 or PSMA expression to explore whether there might be any effective targeted nuclear therapy. F-18-FDG, Ga-68-DOTATATE, and Ga-68-PSMA-11 PET/CT scans were obtained, all of which revealed tracer avidity in extensive locoregional disease. A large, ill-defined retropharyngeal and retrotracheal soft-tissue mass was seen to be eroding the cricoid cartilage and extending into the tracheal lumen and the left-sided strap muscles. In contrast, there was no definite uptake in the multiple lung nodules that were present bilaterally. The scan findings indicated a differential tumor biology between locoregional and distant metastasis.