Aggressive Papillary Thyroid Carcinoma with Bilateral Internal Jugular Vein Invasion Initially Misdiagnosed as Nodular Goiter: A Multimodal Imaging and Molecular Case Report.

INTRODUCTION/BACKGROUND: Papillary Thyroid Carcinoma (PTC) usually has an indolent course, but diffuse aggressive variants can mimic benign nodular goiter and lead to delayed diagnosis. Bilateral Internal Jugular Vein (IJV) invasion with tracheal infiltration represents exceptionally advanced disease. This case highlights how multimodal imaging and molecular profiling refine diagnostic and prognostic evaluation in such an aggressive PTC with tracheal and vascular invasion.

CASE PRESENTATION: A 65-year-old woman was initially diagnosed with benign thyroid nodules based on ultrasound and CT. Progressive dyspnea prompted reevaluation, during which multimodal imaging including conventional ultrasound, Contrast-Enhanced Ultrasound (CEUS), and contrast-enhanced CT revealed bilateral IJV invasion and tracheal destruction. Surgical intervention and pathology confirmed PTC harboring BRAF V600E and TERT promoter mutations. Early postoperative recurrence was observed. The patient underwent radical thyroidectomy with careful assessment of vascular and tracheal involvement guided by imaging findings. Multimodal imaging and molecular profiling informed surgical planning and postoperative management. Postoperative recovery was initially uneventful, with short-term follow-up showing no further immediate complications. Early recurrence emphasizes the aggressive nature of this tumor, while molecular findings provided prognostic insight.

CONCLUSION: Diffuse aggressive PTC can mimic benign nodular goiter, leading to diagnostic delays. "Second-look" multimodal imaging combined with molecular analysis is essential for accurate diagnosis, risk stratification, and management planning. This case underscores the clinical importance of vigilance for vascular and tracheal invasion in PTC, particularly in atypical presentations.