Squamous cell carcinoma (SCC) and Keratoacanthoma

Latest update 16/06/09

This chapter is set out as follows:

• Aetiology of squamous cell carcinoma (SCC)
• Key diagnostic features of SCC
• Keratoacanthoma
• Management of SCC

Aetiology of squamous cell carcinoma (SCC)

• Men are more affected than women
• Genetic factors play a role and individuals with fair skin, blue eyes and blond hair are at higher risk
• Excessive exposure to sunlight is the main aetiological factor and hence incidence increases with age
• Artificial ultraviolet light exposure used in therapy (UVB and PUVA) and sun beds increase the risk
• Patients with xeroderma pigmentosum, albinism or epidermolysis bullosa can develop lesions at a very young age
• Patients on immunosuppressive therapy following kidney or other organ transplant are at a very much higher risk of developing SCC and such lesions tend to behave more aggressively
• SCC can arise in areas of chronic skin inflammation such as leg ulcers
• In pipe smokers the increased risk may be secondary to heat damage

Key diagnostic features of SCC

• Age - mainly found in older patients, although immunosuppressed patients and other high-risk groups referred to above (xeroderma pigmentosum etc) can develop lesions at a much younger age
• Distribution - predominantly arise on sun-exposed sites. The most commonly affected areas are the backs of hands and forearms, upper part of the face and especially in males the lower lip and pinna. There are often other signs of sun-damaged skin
• Lesions may start de-novo or from arise from pre-existing skin lesions such as AK and Bowen's disease
• Transformation can also occur in areas of chronic inflammation such as leg ulcers, and rarely from epidermal naevi and the naevus sebaceous (although BCC transformation is much more common in the latter)
• Most lesions are symptomatic and patients may report pain, bleeding or sensory changes
• In the vast majority of cases the first clinical signs are that of induration and this may take on the following characteristics:
  • Nodular
  • Plaque-like
  • Verrucous
  • Ulcerate
• The surrounding tissue is often inflamed
• Palpation – lesions feel firm when pressed between the thumb and index finger. The limits of induration are not sharp and usually extend beyond the visible margins of the lesion
• Well-differentiated (less aggressive) SCC - Lesions grow slower and are usually papillary with a keratotic surface in the early stages. The keratin tends to be able to be removed quite easily. As the tumour enlarges the balance between keratin production and cellular mass shifts towards cellular proliferation - so even in a well-differentiated tumour the surface tends to ulcerate and growth takes place predominantly at the margins with an increasing area of granulation tissue occupying the centre. This may be shed later to reveal an ulcer or with an indurated, eroded margin (as opposed to a BCC, which looks more punched out) and a purulent exuding surface that bleeds rather easily. The outline is rounded but often irregular.
• Moderate-poorly differentiated (more aggressive) SCC - The organisation of the keratin on the tumour diminishes causing keratin often to be quite sparse or even absent. In an undifferentiated (anaplastic) tumour the stratum corneum may have been replaced by erosion of the surface or frank ulceration. This may appear like granulation tissue and is most commonly seen on the lips and genitalia

Keratoacanthoma (KA)

• KA normally present on sun-exposed skin as pink papules that grow rapidly over a period of about 12 weeks to develop a dome-shaped lesion with a central keratin core. Lesions start to resolve after 3 months. Lesions are often best managed as a low-risk SCC and excised due to the fact that it can be very difficult for histopatholgists to differentiate between KA and SCC, and there have been cases where 'KA' have subsequently gone on to metastasise

Management of SCC

• Suspected or confirmed cases of SCC should be referred to secondary care as a 2-week wait. For more information please click on the following link - 'Improving Outcomes for People with Skin Tumours including Melanoma'
• Also for more in-depth guidelines on SCC please click on the following link - 'Multiprofessional Guidelines for the Management of the Patient with Primary Cutaneous Squamous Cell Carcinoma'

	Figure 1 – Well-differentiated SCC on forearm
	Figure 2 – Two well-differentiated SCC on dorsum of hand The lesion highlighted by the black arrow was obvious. The lesion highlighted by the red arrow was shown to have early changes of an SCC
	Figure 3 – Well-differentiated SCC on dorsum of hand
	Fig 4 – Well-differentiated SCC and a cutaneous horn
	Figure 5 – Well-differentiated SCC on anti-helix Raised irregular nodule (black arrow) with marked keratin (red arrow)
	Figure 6 - Well-differentiated SCC on the cheek This subtle lesion was suspected as being an SCC only after the surface scale was removed to reveal a small red raised and firm lesion
	Figure 7 – Small SCC on top of scalp The lesion was only small but an SCC was suspected as the lesion was raised and firm
	Figure 8 – Moderately-differentiated SCC
	Figure 9 – Poorly-differentiated SCC Note the small amount of keratin
	Figure 10 - Poorly differentiated SCC Note ulceration with lack of any real induration and little keratin
	Figure 11 - SCC on lip arising from leucoplakia
	Figure 12 - SCC lower lip
	Figure 13 - SCC right angle of the mouth
	Figure 14 - SCC affecting the genitalia The risk is increased by chronic inflammatory conditions such as lichen sclerosis or ulcerative lichen planus
	Figure 15 - SCC of the glans penis
	Fig 16 - Keratoacanthoma A well formed dome-shaped lesion with a central keratin core
	Fig 17 - Keratoacanthoma This rapidly growing lesion was not the most classical KA