Skin malignancies

 

Non melanoma skin cancer (BCC and SCC) are some of the commonest types of human malignancy. Up to 80% of these are BCC's with approximately 20% comprising SCC's. The incidence of NMSC's increases with age and whilst there is a female preponderance in those under 40 years of age, in later life the sex incidence is roughly equal.

The vast majority of NMSC's are related to UV light exposure. For SCC's the major pattern is chronic long term exposure.

For BCC's, the pattern of sporadic exposure with episodes of burning is more important. Organ transplant recipients have a markedly increased incidence of SCC, risk factors include length of immunosuppression, ethnic origin and associated sunlight exposure. Human papilloma virus DNA is found in the majority of transplant recipient SCC's. In addition to this increased risk, transplant recipients are also more likely to develop locoregional recurrences following treatment.

Actinic keratosis and SCC

Actinic keratosis is viewed as a premalignant lesion because there are atypical keratinocytes present in the epidermis. In a person with 7 actinic keratosis the risks of subsequent SCC is of the order of 10% at 10 years. The primary lesion is a rough erythematous papule with a white to yellow scale. Lesions are typically clustered at sites of chronic sun exposure.

Squamous cell carcinoma in situ

Also known as Bowens disease the commonest presentation of in situ SCC is with an erythematous scaling patch or elevated plaque arising on sun exposed skin in an elderly patient. Lesions may arise de novo or from pre-existing actinic keratosis.

Pathologically there is full thickness atypia of dermal keratinocytes over a broad zone. Nuclear pleomorphism, apoptosis and abnormal mitoses are all seen.

Invasive SCC

The commonest clinical presentation of SCC is with an erythematous keratotic papule or nodule on a background of sun exposure. Ulceration may occur and both exophytic and endophytic areas may be seen. Regional lymphadenopathy may be present.

Pathologically there is downward proliferation of malignant cells and invasion of the basement membrane. Poorly differentiated lesions may show perineural invasion and require immunohistochemistry with S100 to distinguish them from melanomas (which stain strongly positive with this marker).