A 58-year-old male farmer from rural Maharashtra presents with a 4-month history of a non-healing ulcer on the left buccal mucosa. He reports a 20 pack-year smoking history and chews tobacco with betel nut daily. On examination, the ulcer measures 2.5 cm × 2 cm with indurated, everted margins and a necrotic base. Cervical lymph nodes are palpable on the left side, firm and mobile. Biopsy confirms squamous cell carcinoma. CT imaging shows the lesion confined to the mucosa without bone invasion. What is the TNM stage of this tumor?

Explanation

## TNM Staging of Oral Cavity Carcinoma ### Tumor Size Classification (T-stage) **Key Point:** The TNM staging for oral cavity carcinoma is based on the greatest dimension of the primary tumor: - **T1:** ≤2 cm - **T2:** >2 cm and ≤4 cm - **T3:** >4 cm - **T4a:** Moderately advanced local disease (cortical bone invasion) - **T4b:** Very advanced local disease (masticator space, pterygoid plates, skull base) In this case, the ulcer measures 2.5 cm × 2 cm, which exceeds 2 cm but is ≤4 cm → **T2**. ### Node Status (N-stage) **High-Yield:** For oral cavity carcinoma: - **N0:** No regional lymph node metastasis - **N1:** Metastasis in a single ipsilateral lymph node, ≤3 cm - **N2a:** Metastasis in a single ipsilateral lymph node, >3 cm and ≤6 cm - **N2b:** Metastasis in multiple ipsilateral lymph nodes, all ≤6 cm - **N2c:** Metastasis in bilateral or contralateral lymph nodes, all ≤6 cm - **N3:** Metastasis in a lymph node >6 cm The patient has firm, mobile left cervical lymph nodes (palpable but no size mentioned as >3 cm) → **N1**. ### Overall Stage Determination | T Stage | N0 | N1 | N2 | N3 | |---------|----|----|----|----|----| | T1 | I | II | III | III | | T2 | II | III | III | III | | T3 | III | III | III | III | | T4a | IVA | IVA | IVA | IVA | | T4b | IVB | IVB | IVB | IVB | | M1 | IVC | IVC | IVC | IVC | **T2 N1 M0 = Stage III** [cite:AJCC Cancer Staging Manual 8e] ### Clinical Context **Clinical Pearl:** The presence of lymph node involvement upstages the tumor despite a relatively small primary lesion. This patient would require multimodal therapy (surgery with neck dissection ± adjuvant radiation/chemotherapy). **Warning:** Do not confuse T-stage based on depth of invasion (which applies to other subsites like larynx) with oral cavity staging, which is purely based on greatest dimension.