VivaScope 1500 and 3000 imaging systems for detecting skin cancer lesions

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.

3.17 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.