[Initially palliative, later converted to neoadjuvant therapy in advanced, extensively mediastinal lymphogenous metastatic follicular thyroid carcinoma - a case report].

A 75-year-old female patient presented with persistent cough and exertional dyspnea. Initial CT imaging revealed extensive mediastinal lymphadenopathy associated with a suspicious right-sided thyroid nodule and bilateral cervical lymph nodes.Fine-needle aspiration confirmed follicular thyroid carcinoma with cervical lymphogenous metastases. Molecular analysis detected no actionable mutations. FDG-PET-CT demonstrated multiple mediastinal and bihilar lymph node metastases and a small osseous metastasis in the left iliac bone.Advanced follicular thyroid carcinoma with extensive mediastinal lymphatic metastases and no curative treatment option.Following multidisciplinary tumor board discussion, palliative therapy with the tyrosine kinase inhibitor (TKI) lenvatinib was initiated. After eight months of treatment, a marked reduction in mediastinal tumor mass enabled total thyroidectomy with lymphadenectomy. Subsequently, adjuvant radioiodine therapy (5.5 GBq I-131) was performed. Histology revealed an anaplastic thyroid carcinoma with partial squamous differentiation. Six months postoperatively, due to metastatic progression, systemic combination therapy with lenvatinib and pembrolizumab was started. The patient remains in stable general condition under this regimen.In selected cases, initially palliative TKI therapy can lead to a neoadjuvant effect and enable a curative approach. Continuous multidisciplinary management and close follow-up are essential for successful outcomes.