3 Clinical need and practice
3.1 The purpose of this assessment is to assess the clinical and cost effectiveness of the VivaScope 1500 and 3000 imaging systems to:
help decide whether to biopsy and excise skin lesions in people with suspected skin cancer
define the margins of skin lesions for excision in people with skin cancer.
3.2 Skin cancer is commonly classified into 2 main categories, which include over 95% of all reported skin cancers: melanoma skin cancer and non‑melanoma skin cancer. Melanoma skin cancers develop from melanocytes, the skin cells in the deeper layers of the epidermis that produce the skin‑darkening pigment known as melanin. Non‑melanoma skin cancers develop from keratinocytes, the cells that produce the skin structural protein called keratin.
3.3 Although uncommon, melanoma incidence rates increased 7‑fold between 1976 and 2009. In the UK, it is most common in people 50 years and over. A fifth of cases occur in young adults. The rise in incidence may be a result of increased surveillance, but it is estimated that more than 80% of cases are linked to UV exposure related to recreational behavioural change involving sun exposure and sunbeds (Cancer Research UK 2014). The incidence of melanoma is lower in lower socio‑economic groups.
3.4 Melanoma can invade nearby tissue and spread to other parts of the body. It is responsible for most skin cancer deaths; in the UK in 2010 there were approximately 2200 deaths and 12,818 new cases. Survival has improved substantially in recent decades and the survival rate is among the highest of any cancer, largely because of increased awareness, earlier diagnosis and better treatments (Cancer Research UK 2014).
3.5 Treatment is more likely to be successful when melanoma is detected in its early stages. In the UK, most melanomas are diagnosed at an early stage: 82% in men and 87% in women presented at stages 1 or 2 in 2010. In men, most melanomas present on the trunk (41%), head and neck (22%) or arms (19%). In women the most common sites for presentation are legs (39%), arms (24%) and trunk (20%).
3.6 Melanomas may be classified into broad types (superficial spreading melanomas, nodular melanomas, lentigo maligna melanomas, acral lentiginous melanomas) depending on their growth characteristics, appearance and location on the body.
3.7 Non‑melanoma skin cancers are a group of common cancers, estimated to be about a third of all cancers detected in the UK. In 2011, 102,628 cases of non‑melanoma skin cancer were recorded in the UK. However, the true number of cases may be higher because not all cancers are recorded by the cancer registries. The 2 most common types of non‑melanoma skin cancer are basal cell carcinoma and squamous cell carcinoma. Basal cell carcinoma develops in keratinocytes deep in the epidermis and around the hair follicles; squamous cell carcinoma develops from keratinocytes elsewhere in the skin. Other types of cell in the epidermis may also become malignant, although they are far less common and include Kaposi's sarcoma, Merkel cell carcinoma and T‑cell lymphoma.
3.8 Of the 2 types of non‑melanoma skin cancer, squamous cell carcinoma is the more serious; basal cell carcinoma is rarely fatal. However, if basal cell carcinoma is not diagnosed early enough, or is not properly treated, it can destroy parts of the body such as the nose, eyes, ears and lips, which can be more difficult to treat and may become inoperable. Squamous cell carcinomas can also be disfiguring and, if they spread, fatal.
3.9 Squamous cell carcinoma is the second most common skin cancer with 26,000 cases in the UK in 2011, and its incidence is increasing. Chronic ultraviolet light exposure is a key risk factor and squamous cell carcinoma is commonest in people with sun‑damaged skin. This cancer most often develops in areas that have been exposed to the sun, such as the head, neck, forearms and the backs of the hands. Some squamous cell carcinomas can be difficult to view using imaging techniques because their upper surface is often scaly, which can make it hard to get sufficient resolution (detail).
3.10 Basal cell carcinoma is the most common skin cancer. About 75 out of every 100 cases of non‑melanoma skin cancers diagnosed are this type – approximately 76,000 cases in the UK in 2011. It is most likely to develop in sun‑exposed areas of skin, such as the nose, forehead, cheeks, back or lower legs, and is most often diagnosed in people in middle or older age.
3.11 Basal cell carcinomas (also known as rodent ulcers) may begin as a small lump and usually have shiny or pearly looking edges with a depressed center, which may become crusty or ulcerate. If untreated the ulcer can grow, becoming wider and deeper and affecting more skin tissue. Rodent ulcers can also affect other types of tissue, such as cartilage or bone. However, advanced rodent ulcers are uncommon in the UK because most people get treatment at an early stage.
3.12 There are different subtypes of basal cell skin cancers, including nodular (the most common – around 50% of all basal cell carcinomas), superficial, morphoeic and pigmented. Each of these subtypes looks and behaves differently.
3.13 It is unusual for basal cell skin cancer to spread to another part of the body to form a secondary cancer but it is possible to have more than 1 basal cell skin cancer at any 1 time. People who have already had 1 basal cell carcinoma are at greater risk of developing subsequent basal cell carcinomas.
3.14 Most skin lesions will first be examined in a primary care setting. Because melanoma is still a relatively infrequent cancer in primary care, the initial diagnosis of suspicious skin lesions in primary care should follow the British Association of Dermatologists' ABCD-Easy guide to checking your moles (2011). NICE's guideline on the recognition and referral of suspected cancer (2015) includes a 7‑point checklist that helps clinicians decide whether a person should be urgently referred to a specialist for an appointment under the 2‑week rule, (where urgent referrals to a specialist should be seen within 2 weeks).
3.15 Any lesions that cannot be considered definitively or unequivocally non‑cancerous should be referred to a skin specialist. NICE guidance on improving outcomes for people with skin tumours including melanoma (2010), recommends that health professionals who knowingly treat people with any type of skin cancer should be members of a multidisciplinary skin cancer team (local hospital skin cancer multidisciplinary teams or specialist skin cancer multidisciplinary teams).
3.16 NICE's guideline on the recognition and referral of suspected cancer (2015) recommends that a person with suspected non‑melanoma skin cancer presenting in primary care should be referred for specialist opinion either under the 2‑week rule (squamous cell carcinoma) or as a routine referral. All people who present in primary care with a possible cutaneous squamous cell carcinoma should be referred urgently under the 2‑week rule to a skin specialist, as in the case of suspected melanoma. Basal cell carcinoma should be referred as a routine referral, although low‑risk basal cell carcinoma can be managed in a community setting by a suitably qualified level 1 practitioner (GP).
3.17 The management of cutaneous melanoma is outlined in the British Association of Dermatologists' revised UK guidelines (Marsden et al. 2010). When a person with a suspicious skin lesion presents and there is a need to exclude melanoma, the lesion will usually be examined using a dermatoscope (a handheld, specialised magnifying device). The lesion is photographed and then the whole lesion, together with a clinical margin of 2 mm of normal skin, is completely removed (excision biopsy). This allows tumour staging by measuring the thickness of the tumour in the tissue (Breslow thickness).
3.18 Shave biopsies, which only remove part of the lesion, may be done on large lesions, but this can increase the risk of sampling error and may make staging the tumour difficult. Punch biopsy or incisional biopsy is occasionally used, for example, in the differential diagnosis of lentigo maligna or of acral melanoma. These types of biopsy are only carried out by the skin cancer multidisciplinary team.
3.19 All suspected melanoma lesions that are removed should be sent for histopathological review to the pathologist associated with the specialist skin cancer team. Histological reporting should follow the requirements set out in the British Association of Dermatologists' guidelines for managing cutaneous melanoma (Marsden et al. 2010).
3.20 If it is not possible to distinguish pathologically between a melanoma and a benign melanocytic lesion, the person should be referred to the specialist multidisciplinary team for clinical and pathological review.
3.21 Surgery is the only curative treatment for melanoma and, if there is histopathological confirmation of malignancy, a wider and deeper margin is excised to ensure complete removal. The lateral margins for excision depend on the tumour thickness.
3.22 Lentigo maligna and other in situ melanomas with no potential for metastatic spread should be excised completely with a clear histological margin. No further treatment is necessary. Complete removal is recommended because of the risk of sub‑clinical microinvasion. Incisional biopsy may miss this because of sampling error. Lentigo maligna can present a diagnostic challenge because it can cover a large area on sites such as the face, and have varied histology and diffuse boundaries. In older people the risk of progression may be low, so treatments other than surgery such as radiotherapy or observation may be more appropriate. About 5% of people have a local recurrence within 2 years, possibly caused by incomplete removal of cancer cells around the margin of the excision.
3.23 Diagnosis is established histologically after biopsy and the margins of excised tissues may be stained before histological preparation to determine the peripheral and deep margins. Most squamous cell carcinomas are low risk and respond to several treatments. However, identifying the high‑risk cases needs to be managed by a specialist skin team.
3.24 The aim of treatment is to remove the primary tumour and any metastases. This needs accurate margin assessment. The gold standard for margin identification is currently histology. However, most treatments rely on clinical judgement, which may not accurately predict the extent of the tumour if there is no well‑defined margin.
3.25 The British Association of Dermatologists' guidelines for managing primary squamous cell carcinoma (Motley et al. 2009) state that, when feasible, surgical excision techniques (including Mohs surgery) should be considered as the first choice for treating squamous cell carcinoma, because these techniques provide histological confirmation of tumour removal. Mohs microsurgery involves the removal of tumours to predefined margins, carefully mapped to match the histopathology. The tissue removed from the tumour is histologically examined to identify the further areas of tissue to be removed. This process is repeated until the margins are shown to be clear of cancer cells, and it needs well‑integrated surgical and histological services.
3.26 In surgical excision, a minimum margin of 4 mm is recommended for clinically well‑defined, low‑risk tumours. A narrower margin is more likely to leave residual cancer cells, which can cause recurrence. Ill‑defined tumours more than 2 cm in diameter, tumours that are moderately or poorly differentiated, or tumours on the ear, lip, scalp, eyelid or nose should be removed with a wider margin of 6 mm or more or with Mohs surgery. The concept of clinical margin is important in predicting successful excision.
3.27 Low‑risk nodular basal cell carcinoma may be removed in community settings by suitably qualified GPs. However, if there is uncertainty in the diagnosis or the appropriate treatment cannot be provided in primary care, referral should be made to the specialist skin cancer team according to the NICE guideline on improving outcomes for people with skin tumours including melanomas. Basal cell carcinomas would usually be referred from primary care as a non‑urgent referral rather than by the 2‑week wait rule.
3.28 After diagnosis, basal cell carcinoma may be treated non‑surgically through medical treatments such as imiquimod, or by curettage, cautery or laser ablation. However, higher‑risk basal cell carcinomas may need a more aggressive approach involving surgical removal to clear margins, either by excision or by Mohs surgery. Incomplete excision increases the risk of recurrence. Mohs surgery is a successful treatment for high‑risk basal cell carcinoma and for high‑risk recurrent basal cell carcinoma.