The skin is a prime target for aberrant growth and tumour formation. It may be in direct contact with ionizing radiation and many chemical substances or microorganisms that may act as inducers of abnormal cellular activity. There are also a large number of different cell types represented within the skin. Many skin tumours are rare and in practice are confined to a few types.
Melanocytic naevus (naevocytic naevus)
This is a tumour produced by cells of neural crest origin, mainly melanocytes. Schwann cells may also contribute to the dermal aspect of these lesions. This is the most common type of skin tumour. It is pigmented and is referred to as a ‘mole’ in lay terms. These turn ours originate as a proliferation of melanocytes at the epidermodermal junction, so that clinically little growth above the skin surface is seen at this stage (junctional naevus).
With time, cells migrate downwards into the dermis and their bulk increases so that tumours become elevated above the skin surface. Both an epidermal and dermal component are now seen (compound naevus). Gradually the epidermal component becomes less obvious and the tumour becomes a cellular naevus; fibrotic changes and a loss of pigment may then cause a lesion to become less evident or disappear.
Such lesions may be present in childhood but they appear more obvious and increase their numbers with puberty. Sun-sensitive individuals tend to produce greater numbers, particularly on exposed areas of skin. There is therefore a greater number over the lateral aspect of the arm compared with the medial side. Pregnancy will also increase the numbers of naevi and the degree of hyperpigmentation. he average count of melanocytic naevi on a Caucasian from the Western Hemisphere is more than a dozen by the third decade. Junctional naevi and malignant melanomas should be differentiated by size, the even degree of pigmentation, the smoothness of the overlying epidermis and lack of symptoms in the former. Congenital melanocytic naevi are often bigger and may cover large areas of the skin, e.g. as a bathing trunk aevus. These have an irregular surface and an uneven degree of pigmentation. There is an increased potential for malignant change with larger lesions.
Juvenile melanoma (Spitz naevus)
These naevi are solitary pink or reddish-brown lesions on the face or limbs of children. A history of rapid growth is given and for this reason they are often removed.
A proliferation of naevus cells in the dermis may give rise to blue discoloration of the skin. The mongolian spot in children represents a more diffuse spread of such cells. When these are localized to form a slightly elevated papule, especially in adults, they are called a blue naevus. Basal-cell papilloma (seborrhoeic wart)
This is a benign proliferation of basal cells that produces a raised lesion with a varying degree of pigmentation. The number of these tumours increases with age. The consistency is often greasy and this aspect has led to the misnomer ‘seborrhoeic wart’ -the lesions are not related to sebaceous tissue growth. ‘Senile wart’ is another unacceptable term because the lesions may be seen in young adults.
The face and trunk are the sites most commonly affected. Marked hyperpigmentation may cause confusion with malignant melanoma. Maceration of these tumours from sweating may, in summertime, lead to irritation. The numbers present on the trunk may prohibit their removal in some patients, but readily traumatized or irritant lesions can be removed with a curette and the base cauterized, or they may be frozen with liquid nitrogen.
This rapidly growing tumour of the epidermis arises most commonly on the skin of the hand and face. The aetiology is unknown; it is possible that trauma initiates the event and viral DNA has been shown in these tumours. There is often evidence of chronic actinic damage of the surrounding skin (Fig. 20.20). The lesions are often pale or flesh-coloured, welldemarcated papules and on occasions appear inflammatory. Usually 0.5-1 em in diameter, they may reach 3- 4 em across in giant lesions. The increase in size is rapid and often alarming to the patient. The greatest diameter is attained in 4-8 weeks; involution then occurs and the centre becomes a keratinous crater. Regression may then become complete over several months but, since a ragged scar may be left, it is often better to remove the tumour by curettage. Histological sections may reveal changes that are difficult to differentiate from a squamous carcinoma.
Capillary naevus (naevus flammeus)
This is associated with a proliferation of capillaries in the superficial dermal capillary plexus. The salmon-coloured patch may be seen on the face or more commonly on the nape of the neck in up to 40% of infants. They may not fade from the latter site and are often covered by hair. Facial lesions occur on the glabella, forehead and eyelids and tnd to fade away in the first year of life.
This is a tumour present at birth that consists of dilated capillary vessels with endothelial cell lining. The face and neck are most commonly affected and there is no natural regression with age. Those patients who experience such growths around the orbit may have in addition a proliferation of vessels on the meninges (Sturge-Weber syndrome) and neurological defects. Camouflage is the only practical method of managing such lesions. Laser therapy is time-consuming, is only available at a few centres, and the best results appear to follow the treatment of such naevi in adults.
Cavernous haemangioma (strawberry naevus)
This tumour is not present at birth, but usually appears in the first month of life. Lesions are often well-circumscribed, round and lobulated and are usually seen on the face, neck or trunk. Growth continues in the first year in many patients; this is followed by slow involution, which is complete in the majority by 4-5 years, so that reassurance is often all that is required. Gross lesions warrant attempts at treatment when, for example, they obstruct the eye and threaten the development of binocular vision. The bulk of such tumours may be reduced by systemic steroids or sclerosants. Some naevi show features of both capillary and cavernous tissue within a single tumour. Cherry angioma (Campbell de Morgan’s spot) Campbell de Morgan’s spots are angiokeratomas that appear as pin-point lesions or naevi of several millimetres in diameter on the trunk or limbs with an increasing frequency throughout middle-age. Treatment is only required for cosmetic reasons; cautery or diathermy is effective.
This turnour is a proliferation of dermal vasculature, so that the previous term pyogenic granuloma is a misnomer. Often traurna will initiate this growth on the finger or elsewhere on the skin. In children the trunk is a common site of involvement and there is a tendency for recurrence here from a deep-feeding vascular channel. Bleeding after trauma is a troublesome and worrying feature for some patients and older lesions may become fibrotic. Treatment is by curettage and cautery.
This may appear as a single lesion unassociated with any other developmental abnormality or may occur together with, for example, neurological defects as part of a syndrome. Histologically, there is a proliferation of epidermal structures that are often mixed, so that verrucous, sebaceous, apocrine, eccrine or follicular changes may alloccur. The predominant component will determine the clinical appearances. Some types of naevi may undergo malignant transformation, though this is not common. Sebaceous naevi appear most frequently on the scalp as flesh-coloured, leaf-shaped tumours, which may with time undergo malignant transformation to form basalcell carcinomata.
This tumour is composed of blood vessels, histiocytes or dense fibrous tissue, according to the age of the tumour. It usually arises from traurna such as insect bites and is a common turnour on the legs or buttocks of adults, especially females. A firm tender papule develops, forming a button-like tumour on the surface of which the overlying skin can be wrinkled. The brown pigment or rapid growth may cause alarm and confusion with melanoma.
There is public concern about the increased numbers of malignant turn ours of the skin and their association with sun exposure. Metastases to any part of the skin can occur from many primary carcinoma sites including breast, stomach, lung and kidney.
Basal-cell carcinoma (rodent ulcer)
This is the most common cancer of the skin and is frequently seen on the face of middle-aged or elderly people in the UK, especially those with fair hair and blue eyes who are sun-sensitive and often of Celtic origin. Such
turnours are seen at a younger age in those living nearer to the equator, but the reasons why turnours appear with such frequency on sites such as the periorbital skin, which is to some degree protected from sunlight, is not clear. Other types of ionizing radiation such as X-rays, for example given to young adults for ankylosing spondylitis, have in the past produced sufficient stimulus for the development of basal-cell carcinomata at the irradiated site after a prolonged interval of 10-20 years. Arsenicals may also cause cutaneous malignancy after a similar induction time.
Lesions are most commonly seen at the sides of the nose and around the orbit as flesh-coloured translucent papules or plaques with superficial dilated blood vessels coursing over the surface; central necrosis with ulceration or crusting is frequent (Fig. 20.21). Scarring or cystic or pigmented lesions are less common. There is a tendency for basal-cell carcinomas to be locally invasive but metastasis is extremely rare.
Basal cell carcinomata and lesions appearing as small brown pigmented papules, which are often numerous, are seen in the basal cell naevus syndrome. Superficial scarring and morphoeic basal cell carcinomas are more difficult to discern at their margins from normal skin; although uncommon they are important as they tend to follow tissue planes and invade an orifice such as the orbit. Treatment with X-rays is less effective
for such tumours.
Tumours are normally removed surgically or treated with cryotherapy or radiotherapy. However, lesions that become invasive or are less accessible to normal treatments may be removed by chemosurgery. In Moh’s method the tissue is fixed in situ and excised in a systematic fashion and examined immediately under a microscope to determine the presence or absence of tumour.