Background <p>Giant retrosternal goiter may extend to the carina or below while remaining biologically benign. The main operative challenge is not size alone but whether the mediastinal component can be safely mobilized under direct control of the airway, inferior vessels, recurrent laryngeal nerve (RLN), and parathyroid blood supply. We report two elderly patients with carina-level giant retrosternal goiters to illustrate individualized surgical route selection between a cervical incision alone and a cervical incision with selective T-shaped extended.</p> Case presentation <p>Two women aged 74 and 81 years underwent surgery for giant retrosternal goiter in 2025. Both underwent contrast-enhanced CT of the neck and chest, thyroid function testing, anesthetic assessment, multidisciplinary operative planning with thoracic surgical support, and preoperative blood typing and cross-matching with blood products available according to institutional protocol. In Case 1, the goiter had a substantial cervical component and extended to the carina. Complete resection was achieved through a cervical incision, but focal RLN transection occurred during difficult inferior-pole/thoracic-inlet dissection and was repaired immediately by end-to-end anastomosis. In Case 2, most of the goiter was retrosternal with minimal cervical bulk and extended approximately 1&#xa0;cm below the carina. T-shaped extended cervical incision was added to improve exposure, allowing controlled complete resection with RLN preservation. Estimated blood loss was less than 150 mL in both patients. Final pathology confirmed nodular goiter. At 3 months, Case 1 had impaired right vocal-fold movement on laryngoscopy but no obvious hoarseness, subjective voice dissatisfaction, choking, or clinical aspiration. Case 2 had no significant laryngoscopic abnormality or voice/swallowing complaint. Both patients had no respiratory compromise, clinically significant calcium/PTH abnormality, symptomatic hypocalcemia, or clinical recurrence during short-term follow-up.</p> Conclusions <p>These two cases illustrate the need for individualized surgical route selection in carina-level giant retrosternal goiter. A cervical approach may be reasonable in selected patients when the lesion remains continuous with the cervical thyroid and the mediastinal component, inferior vessels, RLN, and parathyroid glands can be controlled safely under direct visualization. A T-shaped extended cervical incision is an effective adjunct when cervical exposure is inadequate, especially in elderly patients with a deep mediastinal component and minimal cervical bulk. Careful management of the recurrent laryngeal nerve, protection of the parathyroid blood supply, and intraoperative willingness to customize the exposure are essential for achieving complete resection with low morbidity.</p>