Track: Case Reports

Abstract:

Squamous cell carcinoma is the second most common cutaneous malignancy in the U.S., with incidence rising with ultraviolet exposure, aging populations, and immunosuppression. While most are localized and cured surgically, a growing subset exhibits high-risk features such as large size, deep invasion, poor differentiation, and perineural involvement and are prone to regional and distant metastases. In these cases, interventions are challenging and associated with disfigurement, functional impairment, and mortality. Recent approvals of PD-1 inhibitors have expanded options for advanced disease, but real-world data on neoadjuvant use remain limited. We present a 65-year-old man with a rapidly enlarging posterior axillary mass and radiographically suspicious axillary nodes. Biopsy showed poorly differentiated cutaneous SCC (positive pancytokeratin, negative Mart1, CK7, CK20). After multidisciplinary review, he received four cycles of neoadjuvant cemiplimab, which was well tolerated and led to marked tumor regression. Alongside wide local excision with 2-cm margins, sentinel lymph node biopsy was performed to address occult disease risks. Final pathology showed complete pathologic response with no residual tumor and negative sentinel nodes. Therefore, further intervention was determined to be unnecessary. At 3-month follow-up, the patient remains without evidence of recurrence. This case highlights the potential of neoadjuvant PD-1 blockade to achieve complete pathologic response in high-risk cutaneous SCC, enabling surgical de-escalation and avoidance of side effects of adjuvant and systemic therapies. Importantly, it adds to the limited literature describing the microscopic features of cemiplimab response. Further research on cemiplimab target populations and response patterns is needed to update and standardize treatment algorithms.

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Hong Wu