Squamous cell carcinoma is the second most common form of skin cancer, accounting for around 20% of cutaneous malignancies. It is a tumour of epidermal keratinocytes, with the majority arising from actinic keratoses, while the reminder arise de novo. They can grow rapidly and can metastasize. They usually present on sun-exposed skin.
Squamous cell carcinomas begin as skin-coloured, erythematous papules and plaques that develop into nodules. The lesions are often tender and can be associated with a significant degree of thickness. The most frequent physical sign of squamous cell carcinoma is induration (thickening at the edge or base of the lesion, which represents dermal infiltration). Ulceration usually occurs if the lesion has increased in size.
While most squamous cell carcinomas are nodules, some are ulcers. The majority can be excised by wide excision, although larger and more aggressive lesions may require Mohs micrographic surgery and/or radiotherapy. As squamous cell carcinomas have metastatic potential, patients should be re-examined regularly, especially those presenting with high-risk factors.
Pre-cancerous lesions of the skin which can lead to squamous cell carcinoma are actinic keratoses and Bowen’s Disease. The rate of progression of an actinic keratosis to squamous cell carcinoma is small. Presentation of Actinic Keratoses will vary depending on scale, from thin superficial lesions to thick, hyperkeratotic lesions. Bowen’s Disease (Squamous Cell Carcinoma In-Situ) presents as thin, pink patches or plaques. The rate of progression to squamous cell carcinoma can be as high as 3%.
Surgical Excision: The treatment of choice for squamous cell carcinoma. Depending upon the tumour, as long as there are no associated high-risk features, providing suitable margins will prove most effective.
Curettage and Electro-Dessication: This can be considered to treat low-risk squamous cell carcinomas involving the trunk and extremities. Treatment side-effects include thickened scars, incomplete removal and lack of histological control.
Mohs Micrographic Surgery: This has the highest cure rate of all surgical treatments because the tumour is microscopically delineated until it is completely removed. It is indicated for treatment of the following:
