Which TNM staging parameter is used to classify laryngeal carcinoma as T4b (unresectable disease)?

Explanation

## T4b Laryngeal Carcinoma: TNM Staging **Key Point:** T4b laryngeal carcinoma is defined by invasion through the thyroid cartilage with gross extralaryngeal extension into soft tissues of the neck, making it unresectable and requiring non-surgical management. ### TNM T-Staging for Laryngeal Carcinoma | T Stage | Definition | Resectability | | --- | --- | --- | | **T1** | Tumour confined to one subsites of larynx with normal vocal cord mobility | Resectable | | **T2** | Tumour invades multiple subsites or extends beyond larynx (e.g., vallecula, pyriform sinus) but with normal/impaired cord mobility | Resectable | | **T3** | Tumour with fixed vocal cord(s) or invades postcricoid area, paraglottic space, or inner cortex of thyroid cartilage | Resectable | | **T4a** | Tumour invades through thyroid cartilage and/or invades tissues beyond larynx (e.g., trachea, soft tissues of neck, tongue, epiglottis) | Potentially resectable | | **T4b** | Tumour invades **through thyroid cartilage with gross extralaryngeal extension** into soft tissues of neck, mediastinum, or encases carotid artery | **Unresectable** | **High-Yield:** The distinction between T4a and T4b is **gross extralaryngeal extension**: - **T4a:** Invasion through cartilage but limited extralaryngeal spread → may be resectable with multimodal therapy - **T4b:** Extensive soft tissue involvement, vascular encasement, or mediastinal extension → unresectable, requires chemoradiation or palliative care **Mnemonic:** **CARET** for T4b criteria: - **C**artilage invasion with gross extension - **A**irway/soft tissue involvement beyond larynx - **R**adical extralaryngeal spread - **E**ncasement of carotid or mediastinal involvement - **T**herapy: non-surgical (chemoradiation) **Clinical Pearl:** T4b tumours are considered unresectable because the extensive soft tissue and vascular involvement makes complete surgical resection impossible without unacceptable morbidity. These patients are managed with concurrent chemoradiation or palliative therapy.