Uncommon Presentation of Follicular Thyroid Carcinoma with Scalp and Intracranial Extension - Case report

Background Follicular variant of papillary thyroid carcinoma (FV-PTC) is a distinct subtype of thyroid cancer with intermediate clinical behavior between classical papillary and follicular carcinomas. While generally associated with favorable prognosis, FV-PTC can rarely present with distant metastases, including to the skull and scalp, posing diagnostic and therapeutic challenges. Case Description We report a 51-year-old woman initially diagnosed with primary hypothyroidism and a thyroid goitre, later confirmed as FV-PTC after total thyroidectomy. Three years postoperatively, she developed a painless scalp lump. Magentic resonance imaging (MRI) revealed a large heterogeneously enhancing mass involving bilateral frontal skull bones with bone erosion and extension into scalp tissues, compressing adjacent brain structures without parenchymal invasion. Surgical excision of the scalp mass confirmed metastatic follicular thyroid carcinoma. The patient was managed with levothyroxine replacement and calcium supplementation after receiving radioiodine ablation therapy. Conclusion This case highlights the importance of recognizing late solitary skull and scalp metastases in FV-PTC, which can lead to bone erosion and potential involvement of the brain parenchyma. The complementary use of MRI and computed tomography (CT) is vital for thorough assessment of both soft tissue and bony invasion. Given the risk of intracranial extension, management often requires a neurosurgical approach combined with reconstructive surgery to achieve effective tumor resection and restore structural integrity. Long-term surveillance and multidisciplinary treatment strategies remain essential to optimize outcomes in these complex and atypical metastatic presentations.