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

Abstract

We present the molecular 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. ¹⁸F-FDG, ⁶⁸Ga-DOTATATE, and ⁶⁸Ga-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.