Bilateral follicular thyroid carcinoma with large sternal metastasis: Case report and review of the literature

Introduction and importance: Follicular thyroid cancer (FTC) typically spreads hematogenously, with bone metastasis being worrisome, often appearing to be resistant to radioactive iodine (RAI) therapy. Metastasis to sternum is exceedingly rare. Case presentation: A 43-year-old Egyptian male presented with chest tightness, cough, and shortness of breath. He was initially treated as bronchial asthma. Later, he was referred to our thyroid surgery clinic as a case of goitre and palpable sternal mass. He looked clinically well, with enlarged anterior neck mass and visible sternal mass, no lymphadenopathy. Laboratory tests showed thyroid-stimulating hormone levels within normal (2.13 mIU/L), and mildly decreased FT4 (10.3 pmol/L). Neck/chest CT demonstrated multinodular goitre with retrosternal extension, expansile lytic lesion in the sternum, and bilateral lung metastases. Thyroid fine needle aspiration and cytology showed FLUS, and true cut biopsy from the sternal lesion showed invasive FTC. Discussion: Rare bilateral FTC presenting as slow-growing sternal metastasis. The patient underwent total thyroidectomy, followed by high dose RAI therapy, and concluded with sternectomy and reconstruction surgery repair using polymethyl methacrylate wrapped in proline mesh. On follow-up, he received further RAI ablation therapy and became RAI refractory. He then received systemic therapy (Lenvatinib). Most recent follow up showed that the disease was controlled (low volume cancer) and he was tolerating treatment well with no reported symptoms. Conclusion: Bilateral FTC with sternal metastasis is rare, and can be treated with total thyroidectomy, sternectomy and reconstruction, followed by RAI therapy and systemic therapy where required, hence inferring real survival benefit.