A 72-year-old man with a 10-year history of chronic sun exposure and actinic keratosis presents with a 2.5 cm nodular lesion on his left ear with central ulceration. Biopsy reveals poorly differentiated squamous cell carcinoma with perineural invasion. Examination reveals no palpable cervical lymph nodes. CT scan of the head and neck shows no distant metastasis. What is the most appropriate next step in management?

Explanation

## Risk Stratification of This SCC This patient has a **high-risk squamous cell carcinoma** with multiple adverse prognostic factors: | Risk Feature | Present? | Significance | |---|---|---| | **Histologic grade** | Poorly differentiated | High-risk | | **Perineural invasion (PNI)** | Yes | Major adverse feature; increases local recurrence and metastasis risk | | **Location** | Ear (high-risk site) | Ear, lip, and perioral areas have higher recurrence rates | | **Size** | 2.5 cm | Intermediate-to-large | | **Nodal involvement** | Clinically negative | But high-risk for occult metastasis | **High-Yield:** Perineural invasion is a **critical prognostic factor** that mandates aggressive management and staging. ## Why Mohs + SLNB Is Correct ### Mohs Micrographic Surgery 1. **Highest cure rate (95–99%)** for high-risk SCC, especially with perineural invasion 2. **Intraoperative margin assessment** allows real-time visualization of tumor extent and complete margin clearance 3. **Tissue-sparing:** Removes only tumor and minimal normal tissue, important for the ear where function and cosmesis matter 4. **Indicated for:** Poorly differentiated SCC, perineural invasion, facial/ear location, recurrent tumors, immunocompromised patients ### Sentinel Lymph Node Biopsy 1. **Indicated in high-risk SCC** to stage the regional lymph nodes 2. **Perineural invasion** significantly increases the risk of occult regional metastasis (10–20%) 3. **Guides adjuvant therapy:** If SLNB is positive, adjuvant radiotherapy ± chemotherapy is recommended 4. **Prognostic value:** Positive nodes indicate need for close surveillance or completion lymph node dissection **Clinical Pearl:** Unlike melanoma, SLNB in SCC is **not routine** for all tumors—it is reserved for high-risk disease. This patient qualifies due to perineural invasion and poorly differentiated histology. ## Management Algorithm for High-Risk SCC ```mermaid flowchart TD A[SCC with High-Risk Features]:::outcome --> B[Mohs Micrographic Surgery]:::action B --> C[Complete Margin Clearance]:::outcome C --> D{SLNB Performed?}:::decision D -->|Negative| E[Observation + Surveillance]:::action D -->|Positive| F[Adjuvant Radiotherapy ± Chemotherapy]:::action E --> G[Clinical follow-up q3 months]:::action F --> G G --> H[Recurrence-free survival]:::outcome ``` ## Why Each Distractor Is Wrong **Warning:** Standard WLE (even with 10–15 mm margins) is **inferior to Mohs** for high-risk SCC because it lacks intraoperative margin assessment and has higher recurrence rates (10–15% vs. 1–5% with Mohs). **Key Point:** Neoadjuvant chemotherapy is **not standard** for resectable SCC. It is reserved for unresectable, metastatic, or palliative settings. This patient has a resectable tumor and should undergo surgery first. ## Adjuvant Radiotherapy Indications Adjuvant radiotherapy is considered for: - Positive surgical margins (if re-excision not possible) - Positive regional lymph nodes (SLNB or CLND) - Perineural invasion with nodal involvement - Recurrent tumors - Immunocompromised patients with high-risk features In this case, radiotherapy decisions should be made **after** Mohs excision and SLNB results.