Metastatic Squamous Cell Carcinoma Treated With Pembrolizumab in a Patient With Xeroderma Pigmentosum.

A 5-year-old male with xeroderma pigmentosum from Honduras presented with a rapidly growing mass on the left post-auricular neck, associated with left-sided hearing loss. MRI revealed a large mass with invasion of the external auditory canal, temporal bone, and metastasis to lymph nodes. Biopsy confirmed moderately differentiated squamous cell carcinoma (SCC). Given the extensive spread, the patient was started on pembrolizumab, resulting in dramatic clinical and radiographic improvement after four rounds of therapy over 3 months, without associated side effects such as diarrhea, fever, dermatitis, or joint pain. This case demonstrates the effectiveness and tolerability of pembrolizumab in young pediatric patients with metastatic SCC, highlighting its potential as a life-saving treatment for xeroderma pigmentosum patients.