How long should we follow up patients with papillary thyroid carcinoma?: A case report describing brain metastasis after 8 years

RATIONALE: Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer, characterized by favorable prognosis and low incidence of distant metastasis. However, brain metastasis from PTC is rare, and its development years after the initial diagnosis is even more uncommon. Given the potential clinical implications of late metastasis, there is a need to reconsider follow-up strategies for high-risk PTC patients. PATIENT CONCERNS: A 54-year-old woman with a history of PTC diagnosed 8 years earlier presented with progressive headaches and mild left-sided hemiparesis. She had previously undergone multiple surgeries and radioiodine therapy after the initial diagnosis and had a history of childhood neck irradiation. DIAGNOSES: Imaging revealed a brain mass, which was confirmed as isolated brain metastasis from PTC following biopsy after surgical resection. Despite persistently undetectable serum thyroglobulin (Tg) levels and no lymph node metastasis at the time of primary surgery, this patient developed isolated brain metastasis 8 years after initial treatment. INTERVENTIONS: The patient underwent craniotomy to remove the metastatic brain lesion. No adjuvant radiotherapy was given postoperatively. OUTCOMES: The patient recovered well after surgery, with mild left-sided hemiparesis (4/5 muscle strength). At the most recent follow-up, no additional distant metastases were detected. LESSONS: This case highlights the importance of extending the follow-up period for high-risk PTC patients, including those with prior neck irradiation or aggressive tumor features. Late metastasis can occur even in patients with initially favorable prognoses and normal biochemical markers. Imaging-based surveillance is necessary to detect late metastasis early. The findings support extended follow-up strategies to enable timely intervention and improve outcomes in high-risk patients with PTC.