SAT-377 - Acute Suppurative Thyroiditis Revealing Thyroid Invasion by Laryngeal Carcinoma

Background: Acute suppurative thyroiditis (AST) is an uncommon but serious thyroid condition, accounting for < 1% of thyroid disease. It most often results from bacterial infection in individuals with underlying structural thyroid pathology. Although laryngeal carcinoma may extend directly into the thyroid gland in advanced disease, concurrent presentation of AST and tumor invasion is rarely described.

Case Presentation: A 60‑year‑old woman with asthma/COPD, posterior glottic stenosis status post tracheostomy, and recently diagnosed laryngeal squamous cell carcinoma presented with two weeks of neck pain and purulent tracheostomy drainage. Her exam was notable for fever, tachycardia, and marked neck tenderness. Labs were notable for WBC 23,000/µL, TSH < 0.00 mIU/L (0.47–4.68), and Free T4 of 4.88 ng/dL (0.6–2.5). TSI was negative. CT neck demonstrated bilateral complex collections within the thyroid consistent with necrosis or multiloculated abscesses. She underwent ultrasound‑guided abscess drainage. Culture yielded polymicrobial organisms. Cytology revealed atypical keratinizing cells with pancytokeratin and focal p40 positivity, concerning for metastatic squamous cell carcinoma. Beta blockers were not initiated as vital signs were normal. Thionamides were not initiated as thyrotoxicosis was thought to be due to release of preformed thyroid hormone. After antibiotic therapy, symptoms and thyroid function normalized over two weeks. Due to extensive neoplastic involvement, she underwent total thyroidectomy and laryngectomy.

Discussion: AST is rare because of the thyroid’s natural defenses, such as encapsulation, high iodide content, vascularity, and lymphatic drainage. However, infection risk increases with structural abnormalities, malignancy, or immunocompromise. Clinical features include fever, neck pain, and transient thyrotoxicosis. The latter is secondary to dumping of preformed thyroid hormone from the damaged thyroid as opposed to increased thyroid hormone synthesis, and as such, initiation of thionamides would not change the clinical course. Laryngeal carcinoma involves the thyroid in a minority of cases, typically through direct local extension, with cartilage invasion being the strongest predictor. In such cases, thyroidectomy at the time of laryngectomy is often recommended. Importantly, distinguishing true infectious thyroiditis from tumor‑related gland involvement can be clinically challenging, particularly when both coexist.

Conclusion: This case highlights that patients with classic AST may harbor underlying thyroid invasion by laryngeal carcinoma, and the presentation can be accompanied by hyperthyroidism that is typically transient. Clinicians should maintain a high index of suspicion for malignancy, allowing prompt recognition and appropriate surgical and antimicrobial management.

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