Orbital metastasis from thyroid cancer: a case report and review of the literature.

Background: Differentiated thyroid cancer (DTC) is generally associated with an excellent prognosis. However up to 20% of DTC patients have disease events during subsequent follow-up; rarely patients present an aggressive disease with distant metastases (DM), mainly in the lung and bone. Metastases at unusual sites may also occur, generally in patients with disseminated disease. Orbital localization is rare and only few cases have been described so far.
Case Description: A 36 years-old man, treated with chemo and radiotherapy during childhood for non-Hodgkin lymphoma, was referred for suspicious lymph node (LN) and multiple lung metastases. Total thyroidectomy and latero-cervical (LC) lymphadenectomy were performed: papillary thyroid cancer (PTC), 25 mm, 11/17 LN metastases; pT2N1bM1. Post-treatment total body scan with I-131 showed LN and lung uptake. Eighteen months from diagnosis he presented progressive diplopia, proptosis and right exophthalmos due to an 18 mm orbital metastasis. Hence, due to I-131 refractoriness for structural disease progression despite I-131 therapy, he started therapy with Lenvatinib for 6 months, with initial partial response followed by disease progression, and then with Cabozantinib, which he stopped after 6 months for adverse events and disease progression after therapy reduction. Currently, the patient is receiving Lenvatinib, rechallenge therapy, with disease stabilization and biochemical response. Molecular analysis, performed on both primary and relapsed tumor didn't show any significant pathogenic alteration.
Conclusions: This case of DTC with an unusual metastasis in the orbit, may suggest that patient's exposure to chemo- and radiotherapy during pediatric age might have played a role in the subsequent development of this unusually aggressive tumor, reinforcing the recommendation of long-term and intensive follow-up of these patients.