## TNM Staging of Cutaneous Squamous Cell Carcinoma (cSCC) **Key Point:** While perineural invasion (PNI) is a high-risk feature, it does NOT automatically upgrade T stage to T3. It is considered in risk stratification but is not a direct T-stage determinant in the current AJCC system. ### T Staging for cSCC (AJCC 8e) | T Stage | Criteria | |---------|----------| | **T1** | Tumor ≤2 cm; ≤4 mm depth (Clark I–II) OR <4 mm with low-risk features | | **T2** | Tumor 2–4 cm OR >4 mm depth (Clark III–IV) OR ≥4 mm with low-risk features | | **T3** | Tumor >4 cm OR >8 mm depth (Clark V) OR invasion of bone | | **T4** | Invasion of skeleton or deep structures (muscle, cartilage, bone) | ### Depth of Invasion Parameters - **Clark Level**: Histologic depth (I–V) - **Breslow Thickness**: Measured in millimeters from granular layer to deepest tumor cell - **Both influence T staging** ✓ Correct statement ### High-Risk Features (NOT T-stage determinants, but prognostic) - **Anatomic location**: Ear, lip, eyelid, temporal region, genitalia, hands, feet - **Chronic sun exposure areas**: Dorsal hands (as in this case) ✓ Correct statement - **Perineural invasion (PNI)**: High-risk feature, affects prognosis and treatment, but does NOT automatically upgrade T stage - **Poor differentiation**: Grade III - **Depth >4 mm or Clark IV–V**: Influences T stage directly **Clinical Pearl:** PNI is a risk factor for recurrence and metastasis but is NOT a T-stage criterion in AJCC 8e. It may influence treatment decisions (e.g., wider margins, adjuvant therapy) but does not automatically make it T3. ### N and Stage Grouping - **N0**: No regional node involvement - **N1**: Regional lymph node metastases - **N1 + any T, M0 = Stage III** ✓ Correct statement ### Why This Patient is High-Risk - Location: Dorsal hand (high-risk site) - Size: 3 cm (T2) - Ulceration: Suggests deeper invasion - Regional lymphadenopathy: N1 - **Overall: At least Stage III**
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