Axillary Lymph Node Metastasis in Medullary Thyroid Cancer: Atypical Lymphatic Spread or Expression of a Systemic Disease?

Abstract

Medullary thyroid cancer (MTC) is a rare tumor which usually spreads to cervical lymph nodes. Axillary lymph nodes (ALN) involvement is exceptional. We describe the eighth case of ALN metastasis from MTC ever reported and discuss its unusual presentation that suggests the coexistence of undetectable visceral localization.A patient underwent total thyroidectomy with the unexpected finding of MTC when he was 69 years old. For persistent disease, he, afterward, underwent VI level lymphadenectomy, right cervical neck dissection and left cervical lymph node sampling. After 7-years he developed recurrence requiring VI level compartment revision surgery. After that calcitonin levels remained detectable but without any evident relapse at imaging till 2021 when serum calcitonin suddenly and highly increased and 18F-DOPA PET showed a left axillary relapse. A retrograde flow from lymphatics in the neck to the ipsilateral axilla was suggested as possible explanation of atypical spread of ALN. Another explanation is a regular spread of cells from visceral localization in the thorax. In the present case axillary metastases were found in the opposite side of both the primary tumor and the cervical lymph-node metastases. In addition, just after the ALN involvement, the disease showed a more aggressive progression. The high rate of visceral localization reported in patients with ALN metastases from thyroid cancer, together with the evidence, in the present case, of opposite side involvement of lymph-nodes metastases support the idea of an unrecognized visceral spread and a more aggressive behavior of the disease.