Skin cancer. Light micrograph of a section through a basal cell carcinoma, also known as a rodent ulcer. Large numbers of neoplastic cells (blue) have invaded the dermis. Basal cell carcinomas are common tumours of the skin (often the face). The tumour is malignant and locally invasive but slow growing and rarely metastatic.Magnification: x120 when printed at 10 centimetres tall.