A guide to skin cancer of the face for the dental team

Epidemiology

As a group, the NMSCs are far more common than cutaneous melanomas and there were more than 98,000 cases in the UK in 2008.2 Indeed, BCC is the most common cancer in humans and 80% of these present in the head and neck region. These lesions occur most commonly in people aged over 60 years and have a very low propensity to metastasize. There is a genetic predisposition to the development of BCC in patients with Gorlin syndrome (basal cell naevus syndrome; the features of which include multiple BCCs at a young age and keratocystic odontogenic tumours).

Clinical features

Basal cell carcinomas (also known as rodent ulcers) are derived from the basal cell layer of the epidermis and over 90% occur on sun-exposed areas, including the face and scalp. Figure 1 shows the high-risk areas for the development of BCCs on the face. BCCs usually present as slowly-growing, nodular lesions with a pearly raised edge with telangiectasia. There may be a central ulcer if necrosis has occurred (Figure 2). Less commonly, BCCs present as tense, cystic lesions or as an ill-defined, plaque-like morphoeic form (which occur most frequently on the face). BCCs are usually less than 1cm in diameter but, left untreated, will grow and can be locally invasive, with the potential to cause destruction of bone and adjacent organs. However, they only very rarely metastasize to lymph nodes or distant organs.3^,4^,5

Management

The majority of BCCs are treated surgically. Surgery aims to remove the entire lesion plus a margin of normal tissue peripheral and deep to it. The size of this margin is determined by the type and site of the lesion, as well as the presence of adverse histological features indicative of a risk of aggressive behaviour. For example, a nodular basal cell removed with a 4 mm margin will result in a cure in 95% of cases.6 Surgical excision may be followed by primary closure (for small lesions and where the skin can be closed without tension), local skin flaps or skin grafts. Figure 3 shows surgical excision for a BCC of the nose where the surgical defect has been reconstructed with a rotation flap. Figure 4 shows a larger BCC of the nose where the resultant defect has been corrected using a full thickness skin graft.

An alternative to surgical excision for BCCs are the less destructive techniques, including curettage and cautery, and cryosurgery. The obvious limitation of these techniques is the inability to determine the surgical margin and there is, therefore, evidence of higher rates of recurrence for lesions treated in this way.

If patients are unwilling or unable to tolerate surgery, or if the lesion is in an anatomical area that would make surgical reconstruction very difficult, radiotherapy is often the treatment of choice. Complications include damage to adjacent normal skin and other organs (including the eye).

Epidemiology

Like BCC, cutaneous SCC occurs mostly in people aged over 60 years. With an ageing population and a steadily increasing incidence, these lesions are a growing health problem in this country. Exposure to sunlight is the main risk factor for the development of non-melanoma skin cancers. Having a history of one of these lesions increases the likelihood of another. In addition to sunlight, smoking pipes or cigars is a risk factor for developing SCC of the lower lip. Whilst BCCs have a very low propensity to metastasize, the cutaneous SCCs may do and around 500 people die each year from this disease in the UK.2 It is important to emphasize that, in terms of metastatic potential and overall prognosis, SCC of the facial skin has much more favourable outcomes when compared with SCC of the oral cavity.

Clinical features

Squamous cell carcinomas arise from keratinocytes in the epidermis and are also commonly found on sun-exposed areas of the skin. On the face, the high-risk areas are the same as for BCCs (Figure 1) but, in addition, pipe and cigar smoking is associated with SCC of the lip.3 SCCs present as slow-growing lesions of variable morphology and they may arise in an area of actinic keratosis. Actinic keratosis is a potentially malignant lesion that presents as flat or thickened, scaly or reddened areas that represent abnormal skin cell development due to UV radiation. The risk of SCC occurring within an area of actinic keratosis is 10–15%.5 SCCs may also present as nodules or as ulcerated lesions (Figure 5). In contrast to intra-oral mucosal SCCs, those appearing on the skin metastasize much less commonly. Approximately 5% of skin SCCs metastasize and this is most likely if the original SCC was on the lip or ear.5 A dental practitioner noticing a lesion suspicious for cutaneous SCC on the face should, therefore, examine the neck for lymph node involvement. Two important differential diagnoses are worth mentioning here. The first is the keratoacanthoma, which is a common, rapidly-growing lesion with a central keratin plug that resembles SCC clinically. The difference between keratoacanthoma and SCC is that the former will spontaneously involute with time. However, most such lesions will, at least, be biopsied to exclude SCC. The other important differential is the Merkel cell carcinoma which arises from specialized neuro-endocrine cells. These present as painless lesions which may ulcerate. The importance of these lesions is the high mortality rate of around 30%. Figure 6 shows an example of a keratoacanthoma.

Management

As for BCCs, the treatment of choice for cutaneous SCC is surgical excision and reconstruction, where possible. The peripheral margin taken at resection is determined in part by the size of the lesion and usually ranges from 6 mm to 1 cm.7 In addition to excision of the primary lesion, the presence of lymph node metastasis may necessitate the removal of lymph tissue by neck dissection. Figure 7 demonstrates the surgical excision of a SCC from the upper lip and primary closure allowed by the natural laxity of the lip tissue.

In some patients, it is not possible or desirable to perform surgery. For certain types of skin cancer (including BCCs, some SCCs and pre-malignant lesions like actinic keratosis), topical chemotherapy creams or ointments may be used. Examples of such agents include Imiquimod and diclofenac sodium, which are generally applied to the lesion daily for a number of weeks. These drugs are particularly useful where there is widespread skin change, for example, on the scalp of bald men. In addition, radiotherapy has a role in the management of cutaneous SCC.

Epidemiology

Cutaneous malignant melanomas are the least common of the skin cancers but, in the past 30 years, the incidence in the UK has increased four-fold. In 2008, there were just under 12,000 new diagnoses and it is now the sixth most common cancer in both sexes in this country. The disease affects women more commonly than men, but more men die from it. Whilst the majority of cases are in people over the age of 65 years, one-third of patients are under 55 and, in 2008, there were more than 900 cases in those aged between 15 and 34 years. In men, the most common sites affected are the chest and back, whilst the legs are the most common site in women. Overall, between 14 and 22% of malignant melanomas present in the head and neck region. In contrast to many cancers, the incidence of malignant melanoma is higher in more affluent populations and, in the UK, the highest incidence is found in the South-west of England.2

The most important risk factor for the development of malignant melanoma is exposure to sunlight. Factors which further increase the risk include:1

Clinical features

Melanomas develop from melanocytes in the epidermis, but only a minority arise in a pre-existing naevus (mole). In a small proportion, there may be no obvious skin lesion, and the presenting feature may be of lymph node (including in the neck) or distant organ metastasis (usually lung, liver or brain). There are several clinical sub-types of cutaneous melanoma, the most common of which is the superficial spreading type (Figure 8). Other types include nodular and amelanotic (ie lacking pigment) melanomas. Lentigo maligna is a pre-malignant lesion that arises in sun-damaged skin, often on the face, and usually needs treatment as a proportion of these lesions will become invasive. As with any new lesion presenting in the face or mouth, it is important to examine the lymph nodes of the neck thoroughly for possible metastatic involvement.3^,4^,5

When assessing a suspicious pigmented lesion, the ‘ABCDE’ approach is useful (Table 1).5

Management

Once a patient has been referred to a specialist for assessment of a suspicious skin lesion, the first step in the majority of cases will be an incisional biopsy to ascertain the histology. However, this differs for a suspected melanoma where excision of the mole is recommended as this allows for assessment of the depth of the lesion (also known as the Breslow thickness or Clark level). This depth is crucial in determining the margin with which a melanoma is excised and also has prognostic significance. As with the non-melanoma cancers, surgical exicision is the treatment of choice for cutaneous melanoma. However, the surgical margins required to maximize cure are generally much wider, ranging from 1–4 cm depending on the depth of the cancer.8 The potential functional and cosmetic consequences of resection of a large melanoma on or around the face are factors requiring careful discussion with the patient before surgery is carried out. There are no proven benefits of adjuvant therapies for cutaneous melanoma but chemotherapy may be used in the setting of a clinical trial.

The main features of facial skin cancers are summarized in Table 2.