Snapshot A 70-year-old man presents to the dermatologist’s office for his annual skin exam. He complains of a large pink lesion on his cheek that oozes and bleeds. It never seemed to heal properly. He is concerned, because he knows that he should have used more sunscreen throughout his life. Introduction Invasive primary skin malignancy arising from keratinocytes of skin or mucosa Epidemiology common in fair-skinned individuals common in elderly patients 2nd most common form of skin cancer (first is basal cell carcinoma ) risk factors sun exposure actinic keratosis immunosuppression (similar to treatment after organ transplant) arsenic exposure old scars or burns xeroderma pigmentosum ionizing radiation Pathogenesis damage to keratinocytes metastases are rare Keratoacanthoma is a variant of low-grade squamous cell carcinoma grows rapidly and regresses spontaneously Presentation Symptoms typically asymptomatic Physical exam red, poorly defined base with adherent yellow or white scale smooth, dull, red, dome-shaped nodule with ulcerated center frequently on sun-exposed areas face, neck, hands, ears common on lower lips lesions often against a background of sun-damaged skin Evaluation Diagnosis by skin biopsy atypical keratinocytes and malignant cells invasion into dermis keratin “pearls” on histology Differential Diagnosis Actinic keratosis Actinic cheilitis Treatment Surgical wide local excision with negative margins Prognosis, Prevention, and Complications Prognosis if treated, very excellent prognosis Prevention sun avoidance sunscreen use