Skin cancer – Basal cell carcinoma
Malignant skin tumours are among the most common of all cancers. They are more frequent in light-skinned races, and ultraviolet (UV) radiation seems to be involved in their aetiology. The incidence of non-melanoma skin cancer in caucasoids in the USA was recently estimated at 230 per 100 000 per year, compared with 3 per 100 000 for African Americans. The majority of malignant skin tumours (Table 1) are epidermal in origin and are either basal cell or squamous cell carcinomas (p. 100) or malignant melanomas (p. 103). Premalignant epidermal conditions are common (p. 98), but dermal malignancies are comparatively rare.
Table 1 A classification of malignant skin tumours and premalignant conditions
| Cell origin | Premalignant condition | Malignant tumour |
|---|---|---|
| Keratinocyte | Actinic keratosis (p. 119), in situ squamous cell carcinoma (p. 100) | Basal cell carcinoma Squamous cell carcinoma |
| Melanocyte | Dysplastic naevus (p. 103) | Malignant melanoma (p. 103) |
| Fibroblast | Dermatofibrosarcoma (p. 98) | |
| Lymphocyte | Lymphoma (p. 98) | |
| Endothelium | Kaposi’s sarcoma (p. 56) | |
| Non-cutaneous | Secondary (p. 43) |
Aetiopathogenesis
Malignant transformation of basal cells may be induced by:
prolonged UV exposure (and acute sunburn)
immunosuppression (e.g. renal transplant recipients)
arsenic ingestion, e.g. in ‘tonics’ or drinking water
X-rays and other ionizing radiation
chronic scarring, e.g. burns or vaccination scars
