Squamous cell carcinoma:

Squamous cell carcinoma is a more aggressive tumour than basal cell carcinoma as it can metastasize if left untreated. Most relate to sun exposure and daily application of sun cream has been shown to reduce the incidence in Australia. They can arise in pre-existing solar keratoses or Bowen's disease or be due to chronic inflammation such as in lupus vulgaris. Rarely multiple tumours arise because of arsenic ingestion in early life. Multiple tumours occur in people who have had prolonged periods of immunosuppression, such as renal transplant patients where certain human papilloma virus subtypes may be involved in malignant transformation.

Clinically the lesions are often keratotic, rather ill-defined nodules which may ulcerate (Fig. 23.33). They can grow very rapidly. Examination of regional lymph nodes is essential. They are most common on sun-exposed sites in later life. One should have a high index of suspicion for ulcerated lesions on the lower lip or ear.
Treatment is with excision or occasionally radiotherapy. Curettage should be avoided.