What are the stages of cancer of the buccal (oral) mucosa?

Stages of Buccal Mucosa Cancer

Buccal mucosa cancer staging follows the UICC TNM 8th edition classification system, which divides disease into stages I through IVB based on tumor size/invasion (T), nodal involvement (N), and distant metastases (M). 1

TNM Classification Components

Primary Tumor (T) Classification

• T1: Tumor ≤2 cm with depth of invasion (DOI) ≤5 mm 1
• T2: Tumor ≤2 cm with DOI >5 mm and ≤10 mm, OR tumor >2 cm but ≤4 cm with DOI ≤10 mm 1
• T3: Tumor >2 cm with DOI >10 mm, OR tumor >4 cm with DOI ≤10 mm 1
• T4a (moderately advanced): Tumor invades adjacent structures including cortical bone, maxillary sinus, or skin of face 2
• T4b (very advanced): Tumor invades masticator space, pterygoid plates, skull base, or encases the internal carotid artery 2

Regional Lymph Node (N) Classification

• N0: No regional lymph node metastasis 2
• N1: Single ipsilateral lymph node ≤3 cm in greatest dimension 2
• N2a: Single ipsilateral lymph node >3 cm but ≤6 cm 1
• N2b: Multiple ipsilateral lymph nodes ≤6 cm 1
• N2c: Bilateral or contralateral lymph nodes ≤6 cm 1
• N3: Any lymph node >6 cm 1

Distant Metastasis (M) Classification

• M0: No distant metastasis 1
• M1: Distant metastasis present 1

Stage Grouping

Early Stage Disease

• Stage I: T1N0M0 2
• Stage II: T2N0M0 2

Locally Advanced Disease

• Stage III: T3N0M0 or T1-3N1M0 2
• Stage IVA: T4aN0-1M0 or T1-4aN2M0 2
• Stage IVB: T4b (any N) M0, or any T with N3M0 1
• Stage IVC: Any T, any N, M1 (distant metastatic disease) 3

Critical Pathological Features for Staging

On surgical specimens, the following must be evaluated as they significantly impact staging and prognosis: 1

• Depth of invasion (DOI): Critical determinant for T classification in oral cavity cancers 1
• Number of invaded lymph nodes: Independently associated with survival 4
• Extracapsular extension: Presence significantly worsens prognosis and triggers need for adjuvant chemoradiotherapy 1, 4
• Perineural invasion: Independent prognostic factor for overall survival 4
• Lymphovascular invasion: Must be documented 1
• Surgical margin status (R0 vs R1): Critical for determining need for adjuvant therapy 1
• Tumor differentiation: Well-differentiated tumors have significantly better outcomes than poorly differentiated 5

Important Clinical Caveats

Buccal mucosa cancer is particularly aggressive with worse stage-for-stage survival compared to other oral cavity sites. 6 Even T1-T2 tumors demonstrate only 78% and 66% 5-year survival respectively, which is notably poor for early-stage disease 6.

Stage IV disease does not automatically mean incurable disease—Stage IVA and IVB without distant metastases can still be treated with curative intent using aggressive combined modality therapy. 3 However, outcomes remain significantly worse than earlier stages, with Stage IV 5-year survival of approximately 42.6% 4.

The presence of muscle invasion and Stensen's duct involvement are associated with significantly decreased survival and should be specifically assessed. 6