Endocrine Abstracts

Introduction: Medullary thyroid cancer accounts only 1% to 4% of thyroid cancer cases (1). 25% of cases are familial secondary to germline RET mutation, while the remaining 75% are sporadic and also harbour a somatic RET mutation in more than half of all cases. Up to 15–20% of patients will present with distant metastatic disease. The standard treatment for MTC is total thyroidectomy and dissection of cervical lymph node compartments. Post-operative levels of serum calcitonin > 150 ng/l generally indicate distant metastases. We present a case of sporadic RET-negative medullary cancer with distant metastases.

Clinical case: 72 y.o man referred for thyroid USS with neck swelling and supraclavicular lymph node enlargement in March 2023. USS revealed left sided conglomerate of the slightly hypoechoic nodules with internal calcifications measuring up to 51 mm in diameter (U4/5) and rounded lymph node in the left neck measuring 1.6x9.2x11 mm. FNA confirmed suspicious for malignancy (Thy4). CT neck showed extracapsular extension focally anteriorly to the SCM and extensive lymph nodes extending from level 2-6 on the left. After discussion at MDT calcitonin level has been checked which showed 12100 ng/ml. Meanwhile screen for pheochromocytoma, hyperparathyroidism and RET-gene was negative. Subsequently, patient underwent total thyroidectomy with level 6 lymph adenectomy and bilateral neck dissection in June 2023. Repeated calcitonin level in September 2023 showed calcitonin 7380. MRI liver in October 2023 showed multiple bilobar liver metastases which were Dotate-PET negative, but positive on FDG-PET scan. Furthermore, both PET scans showed positive uptake in the left supraclavicular fossa, which is concerning for residual/metastatic disease. Latest calcitonin level is 8770 and after MDT discussion there is plan for tyrosine kinase inhibitors therapy.

Discussion: Medullary thyroid cancer is a rare thyroid cancer with high mortality rate requiring multidisciplinary approach. Our case represent challenges in diagnosis and ongoing care of the patients with medullary cancer. While surgical management is a main treatment approach for medullary cancer, metastatic and recurrent cases can be treated with new treatment modalities, like thyrosine kinase inhibitors.