Medullary thyroid carcinoma - PET/CT imaging with 68Ga-labelled gastrin and somatostatin analogues

a 75-year-old man with a 10-year history of nodular goitre was referred for clinical evaluation. The ultrasound scan revealed enlarged thyroid right lobe almost fully filled with a heterogeneous nodule with numerous calcifications. Fine-needle aspiration biopsy suggested medullary thyroid carcinoma (MTC). Before the surgery the patient was referred to the nuclear medicine department and somatostatin receptor imaging (SRS; 68Ga-DOTATATE) with PET/CT was performed. The scan demonstrated an increased uptake within the right thyroid mass. Subsequent PET/CT with 68Ga-gastrin analogue (MG48) revealed the same indications as the SRS: an increased alveolar uptake in the right thyroid mass without the signs of lymph node metastases. The patient underwent total thyroidectomy and central lymph nodes dissection. Histopathology examination confirmed the presence of MTC with vascular invasion, but without lymph node metastases (pT3NoMx according to the 7th edition of the AJCC Cancer Staging Manual). Immunohistochemical staining revealed positive reaction to calcitonin and CD56, whereas the reaction to thyroglobulin remained negative. The Ki-67 was 1%. Staining for SSTR2 and CCK2 showed high cytoplasmic expression in both cases. Knowledge of the presence of CCK2 receptor in MTC patients may be an important indication for the choice of diagnostic and therapeutic procedures. The presence of both the receptor types, cholecystokinin-2/gastrin and somatostatin, is possibly an interesting combination as far as the therapeutic target is concerned.