IMG-03. Initial presentation of papillary thyroid carcinoma as brain metastasis: a case report

Abstract INTRODUCTION Papillary thyroid carcinoma (PTC) is the most common differentiated thyroid cancer, typically exhibiting an indolent course with a favorable prognosis. Distant metastases occur in approximately 10% of cases, predominantly affecting the lungs and bones. Brain metastases are rare, accounting for less than 1% of cases. An initial presentation of PTC as a brain metastasis, without prior identification of a primary thyroid lesion, is exceptionally uncommon. CASE REPORT A 60-year-old man with a history of seizures presented with right arm weakness and gait imbalance. Brain MRI revealed a 4.5 cm left frontal lobe mass. He underwent a gross total resection and brain radiotherapy. Histopathology and molecular analysis confirmed metastatic PTC with a BRAF V600E mutation. Subsequent PET-CT imaging identified metastatic lesions in the right lung and cervical lymph nodes. Total thyroidectomy with neck dissection, followed by radioactive iodine ablation, was performed. Postoperatively, he experienced complications related to brain surgery and the progression of pulmonary metastases. DISCUSSION Brain metastases from PTC can occur several years after the initial diagnosis; these are often associated with aggressive histologic variants and adverse molecular features, such as BRAF V600E mutations. Clinical presentations can include nonspecific neurological symptoms like headaches, seizures, or focal deficits. Contrast-enhanced MRI is the diagnostic modality of choice. Management involves a multimodal approach, including surgical resection and stereotactic radiotherapy, particularly for patients with solitary, accessible lesions and good functional status. In cases with progressive, radioiodine-refractory disease and multiple metastases, tyrosine kinase inhibitors may offer benefits. Despite these interventions, the prognosis remains poor, with a median survival of 5 to 15 months following diagnosis. CONCLUSION This case highlights the importance of considering metastatic PTC in the differential diagnosis of intracranial lesions, even without known primary thyroid disease. Further studies are needed to establish standardized management protocols for such atypical presentations of PTC.