Rare case of cutaneous cystic squamous cell carcinoma on the forehead

Summary: There is a paucity of literature describing cystic squamous cell carcinoma arising on the scalp or face. We present a case of an 87-year-old male with a past medical history significant for solid organ transplant and concomitant history of numerous squamous cell carcinomas. He presented to our clinic for evaluation of an asymptomatic well circumscribed 2.2cm subcutaneous nodule on his forehead. Given the clinical appearance, a benign preliminary differential diagnosis was considered and a subsequent excision was performed. However, upon review of the histopathology at scanning magnification, the sections demonstrated varying sized squamous islands and squamous lined keratinizing cystic structures in the dermis. The cystic structures contained a dense eosinophilic material and necroinflammatory debris. They were lined by squamous epithelium which demonstrated marked atypia with prominent nuclear pleomorphism. Perineural invasion was not seen. A diagnosis of cystic squamous cell carcinoma arising from squamous cell carcinoma in situ was made. Follow-up imaging revealed no underlying primary head and neck malignancy or metastasis and definitive treatment with Mohs surgery and radiation therapy were initiated. This case highlights the importance of histopathology in the diagnosis of clinically benign appearing lesions and utility for selecting appropriate treatment plans.