Frontal Lobe Metastasis from Papillary Thyroid Carcinoma: A Case Report and Literature Review

Papillary thyroid carcinoma (PTC) is the most common type of well-differentiated thyroid cancer and usually has a favorable prognosis with a low risk of metastasis. However, distant metastasis significantly worsens the prognosis. Brain metastasis of papillary thyroid carcinoma is very rare, and there is currently no standardized treatment protocol for this condition. Case Presentation: A 56-year-old woman was admitted to our hospital 7 years after undergoing total thyroidectomy for primary papillary thyroid carcinoma, presenting with neurological symptoms including decreased mental responsiveness, memory impairment, and motor aphasia. Brain MRI revealed an abnormal mass in the left frontal lobe with extensive surrounding edema. The patient underwent left fronto-temporal craniotomy with complete tumor resection. Postoperatively, the patient showed significant neurological improvement and was started on oral thyroxine replacement therapy. Innovation and Significance: This case provides several noteworthy contributions: (1) It is one of the few reported cases of a single frontal lobe metastatic lesion occurring more than 7 years after primary tumor treatment; (2) It establishes a standardized approach to comprehensive pre- and postoperative neurological assessments; (3) It challenges the traditional view that brain metastases in PTC are almost always associated with extensive systemic dissemination; (4) It provides detailed immunohistochemical characterization of both the primary tumor and the metastatic site. Conclusion: PTC is the most common type of thyroid cancer, typically slow-growing with generally favorable outcomes. Metastases most commonly involve regional lymph nodes, with occasional distant metastases to the lungs and bones. Brain metastases from PTC are extremely rare. In this paper, we present a case of pathologically confirmed PTC brain metastasis in the left frontal lobe and review the available literature on its clinical significance.