A 72-year-old woman presents with a scaly, indurated nodule on the left temple that has grown over 6 months. She has a history of actinic keratosis in the same area. Dermoscopy reveals a hyperkeratotic plug with irregular vascular pattern. Excisional biopsy shows moderately differentiated squamous cell carcinoma with invasion into the subcutaneous fat and perineural invasion. The margins are clear (>5 mm). What is the most appropriate next step in management?

Explanation

## Management of High-Risk Cutaneous Squamous Cell Carcinoma **Key Point:** Moderately differentiated SCC with subcutaneous invasion and perineural invasion is classified as **high-risk**, warranting adjuvant radiation therapy even with clear surgical margins. ### Risk Stratification in Cutaneous SCC | Risk Category | Features | Management | |---------------|----------|-------------| | **Low-risk** | Well-differentiated, <4 mm depth, no perineural invasion, <2 cm, no immunosuppression | Excision alone with 4–6 mm margins | | **Intermediate-risk** | Moderate differentiation, 4–8 mm depth, or minor perineural invasion | Excision + consider adjuvant RT if multiple risk factors | | **High-risk** | Poor differentiation, >8 mm depth, perineural invasion, >2 cm, recurrent, immunosuppressed | Excision + adjuvant RT ± chemotherapy | **High-Yield:** Perineural invasion (PNI) is one of the strongest predictors of recurrence and metastasis in cutaneous SCC. Subcutaneous invasion + PNI = definite indication for adjuvant radiation. ### Why Adjuvant Radiation Is Indicated Here 1. **Subcutaneous invasion:** Tumor extends beyond dermis into subcutis (Clark level V equivalent). 2. **Perineural invasion:** High risk of occult nodal disease and local recurrence. 3. **Clear margins are NOT sufficient:** Even with clear surgical margins, the tumor's biological aggressiveness mandates adjuvant therapy. **Clinical Pearl:** Adjuvant RT to the primary site and first-echelon lymph nodes (parotid and cervical nodes for temple lesion) reduces local recurrence from ~20% to ~5% and improves disease-free survival. ### Why Other Options Are Suboptimal - **Observation alone:** Unacceptable risk of local recurrence and occult nodal disease in high-risk SCC. - **Sentinel lymph node biopsy:** Not standard for cutaneous SCC unless clinically evident nodal disease; elective neck dissection is not indicated without nodal involvement. - **Topical 5-FU:** Appropriate for actinic keratosis and field cancerization, not for invasive SCC with PNI. [cite:NCCN Cutaneous Squamous Cell Carcinoma Guidelines 2023; Robbins 10e Ch 25]