Abstract
Squamous Cell Carcinoma (SCC) is the second most common type of skin cancer. It originates from the epidermal keratinocytes that display variable degrees of differentiation and cytologic atypia. SCC has many histologic variants including basaloid, desmoplastic, papillary, and sarcomatoid carcinoma. SCC with signet ring cell differentiation is extremely uncommon and has been reported in the head and neck region. Signet ring cells are predominantly associated with adenocarcinomas and more aggressive behavior. However, the mechanisms involved in signet ring cell formation in other tumors are still under investigation. Herein, we analyze the case of a 56-year-old female with a history of multiple periocular SCCs, basal cell carcinoma, and one-year treatment with Cemiplimab (programmed death receptor-1 (PD-1) inhibitor) who presents with a new lesion on the face. The patients clinical history does not reveal any other visceral malignancy. At the physical examination, an erythematous scaly papule on the forehead is identified measuring 0.4 cm. The clinical differential diagnosis includes SCC and actinic keratosis. Microscopically, an ulcerated tumor arising from the epidermis is observed, demonstrating lobules of neoplastic epithelial cells with marked nuclear atypia and minimal keratinization infiltrating the dermis and intermixed with signet ring cells. Immunohistochemical studies are performed revealing that both components of the tumor are positive for p63, CK5/6, CDX2, and p53 while negative for p16, CK7, CK20, and CD68 stains. The overall findings support the diagnosis of primary cutaneous SCC. To our knowledge, this case represents the first signet-ring cutaneous SCC that develops during therapy with a PD-1 inhibitor.
Financial Disclosure:
No current or relevant financial relationships exist.
