Refractory Thyrotoxicosis in Oropharyngeal Squamous Cell Carcinoma Invading the Thyroid Gland

OBJECTIVE: Thyrotoxicosis from local invasion of the thyroid gland by an extrathyroidal malignancy is rare. We describe a patient with thyrotoxicosis secondary to invasion of the thyroid gland by an oropharyngeal squamous cell carcinoma (OPSCC). To our best knowledge, this has not been reported. CASE REPORT: A 62-year-old Indian man with histologically proven, p16-negative, cT3N3bM0 (stage IVb) posterior OPSCC was admitted for elective gastrostomy. Biochemical thyroid profile was normal before admission, and there was no thyroid invasion radiologically. The patient developed persistent fever and tachycardia associated with an elevated white cell count and C-reactive protein. This was treated as sepsis, and antibiotic therapy was initiated for 17 days without response. An extensive septic workup did not reveal any infection. A subsequent neck computed tomography revealed rapid progression of the OPSCC, with the invasion of bilateral thyroid lobes. Thyroid function tests revealed primary hyperthyroidism. Antibodies indicative of Graves’ disease were negative. A tracheostomy was performed due to impending airway compromise. The patient showed minimal clinical improvement with medical management, and thyroid function continued to worsen. He died due to cardiorespiratory collapse due to tumor progression, new-onset atrial fibrillation, and poor underlying cardiac function. DISCUSSION: We report a rare observation of thyrotoxicosis secondary to thyroid gland invasion by OPSCC. This highlights the need for a high index of suspicion of malignancy-induced hyperthyroidism and evaluation of thyroid function early in febrile/tachycardic patients with locoregionally advanced head and neck SCCs. Urgent oncological treatment may be necessary to control thyrotoxicosis.