Abstract Introduction Anaplastic thyroid carcinoma (ATC) is an aggressive undifferentiated thyroid malignancy, typically affecting elderly patients presenting with rapidly progressive neck swelling, dysphagia, voice changes, and potentially life-threatening upper airway compromise. Lemierre’s syndrome is a rare complication of an upper respiratory tract infection characterized by septic thrombophlebitis and potential abscess formation. We present a unique case of ATC initially mimicking Lemierre’s syndrome. Case Presentation A 73-year-old female with type 2 diabetes mellitus and hypertension developed an upper respiratory tract infection complicated by presumed Lemierre’s syndrome with right internal jugular thrombosis. She was treated empirically with intravenous antimicrobials, corticosteroids, and anticoagulation.One month later, she re-presented with progressive facial and upper extremity swelling consistent with superior vena cava (SVC) syndrome. Repeat CT imaging revealed thrombus extension from the cavo-atrial junction of the superior vena cava to the jugular foramen, as well as a new 2 cm peripherally enhancing intrathyroidal lesion, initially suspected to represent an abscess. She underwent surgical thrombectomy, and the pathology of the specimen showed tumor thrombus consistent with ATC.Post-operatively, the patient developed worsening facial swelling and respiratory distress with airway compromise requiring fiber-optic awake intubation and MICU transfer. Fine-needle aspiration of the thyroid lesion revealed high-grade undifferentiated thyroid tissue, raising suspicion for ATC rather than abscess formation secondary to Lemierre’s syndrome. Subsequent total thyroidectomy confirmed anaplastic thyroid carcinoma arising from papillary thyroid carcinoma. Given the poor prognosis and multiple subsequent hospital complications, she transitioned to hospice care. Discussion This represents a unique case of ATC presenting as tumor thrombus initially thought to be septic thrombophlebitis from Lemierre’s syndrome. The initial CT soft tissue neck with contrast only showed right jugular vein thrombosis without any thyroid abnormalities. Within three weeks, repeat imaging demonstrated extension of the thrombus and a new thyroid nodule. The rapid progression of this patient’s ATC led to further complications, including respiratory failure and airway compromise. Failure to identify ATC early on can lead to rapid progression and high comorbidity as seen in our case.Although ATC accounts for only 1-2% of all thyroid cancers it represents most of the thyroid-cancer-related mortality due to its rapid progression and limited treatment options.This case underscores the diagnostic challenge posed by ATC mimicking Lemierre’s syndrome when presenting with metastatic thrombosis. Clinicians should maintain a high degree of suspicion for ATC if there is no clinical response to antibiotics in the presence of suspected internal jugular vein thrombophlebitis and worsening neck edema. This abstract is funded by: None
Dacdac et al. (Fri,) studied this question.