Metachronous head and neck osteosarcoma in an elderly patient: A rare case report with prior verrucous carcinoma.

RATIONALE: Head and neck osteosarcoma is a rare malignancy, accounting for 6%-10% of all osteosarcomas, and typically affects younger individuals. Its occurrence as a metachronous tumor in elderly patients, particularly after radiotherapy, is exceedingly uncommon. PATIENT CONCERNS: A 91-year-old man with a history of right lateral tongue verrucous carcinoma treated by surgery and adjuvant radiotherapy (50 Gy) in 2006 presented in 2024 with progressive hoarseness and dysphagia for 6 months. DIAGNOSES: Clinical examination revealed a firm neck mass. Laryngeal biopsy showed benign keratosis, while core needle biopsy demonstrated a malignant mesenchymal tumor with osteoid production. Immunohistochemistry showed negative cytokeratin and p63, and Ki-67 positivity in 20% of cells, confirming osteosarcoma. Imaging revealed a calcified lesion involving the hyoid, thyroid cartilage, and tongue base, consistent with metachronous head and neck osteosarcoma. INTERVENTIONS: Due to advanced age and comorbidities (hypertension and diabetes), palliative radiotherapy (30 Gy in 15 fractions) was administered. Surgery and chemotherapy were avoided because of frailty and limited benefit. OUTCOMES: The patient tolerated treatment well, achieving partial symptom relief without major toxicity. Long-term follow-up continues with a focus on quality of life. LESSONS: This case highlights the diagnostic challenges of secondary head and neck osteosarcoma following radiotherapy and the importance of long-term surveillance in elderly patients. Individualized management balancing treatment efficacy and tolerability is essential in geriatric oncology.