Case Report: Unexpected long-term survival in metastatic anaplastic thyroid carcinoma through multidisciplinary management.

Anaplastic thyroid carcinoma (ATC) is one of the most lethal human malignancies, with a median overall survival of 3 to 5 months and a 1-year survival rate below 20%; survival beyond 2 years remains distinctly uncommon, particularly in patients with metastatic disease. We report a 45-year-old man who underwent left thyroid lobectomy for a mass initially attributed to an inflammatory condition; final pathology revealed an 8.0-cm ATC (pT3bN1a, Stage IVC). Molecular profiling demonstrated BRAF V600E and TERT promoter mutation-negative status, no actionable next-generation sequencing (NGS) targets, and an exceptionally high PD-L1 combined positive score (CPS) of 90. The postoperative course was complicated by progressive wound deterioration precluding radiotherapy. Following multidisciplinary team (MDT) consensus, lenvatinib (20 mg/day) plus pembrolizumab (200 mg every 3 weeks) was initiated on July 12, 2024; wound complications were managed through iterative surgical wound care conducted concurrently with uninterrupted systemic therapy over nine cycles. At the most recent follow-up on July 13, 2026 - 28 months after initial presentation - imaging demonstrated sustained disease control with no evidence of disease progression or newly developed lesions, and the patient remained alive under active surveillance, though with mild residual discomfort from skin adhesion at the prior drain site. This case demonstrates that durable disease control is achievable in selected patients with metastatic BRAF wild-type ATC, and highlights extreme PD-L1 expression as a potential biomarker guiding immunotherapy selection, alongside the critical importance of multidisciplinary coordination enabling treatment continuity despite significant surgical complications.