Skin Cancers: Basal and Squamous Cell Carcinoma

Key points

• • Both are strongly linked to long-term ultraviolet sun exposure: squamous cell carcinoma arises from epidermal keratinocytes, while basal cell carcinoma arises from the basal (germinative) cells of the epidermis and its hair follicles.
• • Basal cell carcinoma is the commonest skin cancer; it typically forms a slow-growing pearly nodule with a rolled edge and fine surface blood vessels, usually on the face.
• • Basal cell carcinoma invades locally and can erode deeply (a rodent ulcer) but almost never spreads to distant sites.
• • Squamous cell carcinoma often forms a scaly or ulcerated lump and can arise in a pre-cancerous patch (actinic keratosis) or in a long-standing scar or ulcer.
• • Squamous cell carcinoma can spread to lymph nodes, so it is more dangerous than basal cell carcinoma, though still less so than melanoma.
• • Both are far commoner in fair-skinned people and at sun-exposed sites, which is why sun protection lowers the risk.