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Chapter 9: Skin tumours 407

Pathophysiology Keratoacanthoma (KA) is a rapidly growing hyper-
Mutations in the tumour suppressor gene and patched keratotic nodule with a central keratin plug. This is
(PTCH) on chromosome 9 have been identified in both probably a low-grade malignancy that originates in
sporadic basal cell carcinoma and familial basal cell ne- the pilosebaceous glands. It is considered by some to
vus syndrome. As with other tumour suppressor genes beavariantofinvasivesquamouscellcarcinoma.Most
bothcopiesneedtobedamagedbeforetumoursdevelop. resolve spontaneously but they may rarely progress to
With the familial form, patients inherit one inactive gene invasive or metastatic carcinoma. Surgical excision is
and are therefore susceptible to tumour development. often advocated.
Only a minority of basal cell carcinomas become locally Bowen’s disease is squamous carcinoma in situ. It ap-
aggressive or metastasise. pears as a red patch or plaque with variable scaling on
sun damaged skin. Such areas require 5-fluorouracil
Clinical features cream, cryotherapy or curettage.
Most basal cell carcinomas occur on the face. And three
patterns are recognised: Clinical features
Nodularbasalcellcarcinomaisthemostcommontype
Mostsquamouscellcarcinomaspresentwithalocallyin-
(60%) appearing as a firm pink-coloured raised nod- vasive and well-differentiated papule, nodule or plaque,
ule,oftenwithtelangiectaticvesselswithinthenodule. which frequently ulcerate if left untreated. Sometimes
Central ulceration is common (rodent ulcer). they have a rolled everted edge. Squamous cell car-
Superficial basal cell carcinoma (30%) occurs on the
cinoma metastasise initially to regional lymph nodes
trunk as a flat scaly red plaque, often with an irregular which should be examined.
micropapular edge.
Morphoeic basal cell carcinoma (10%) is typically flat
Management
smooth, flesh-coloured, or a plaque with indistinct Surgical excision is the treatment of choice; this may ne-
edges. cessitate reconstruction and skin grafting. Lymph nodes
shouldbeexaminedandremovedifinvolved.Radiother-
Investigations apy is an alternative in patients unfit for surgery.
Suspicious lesions are investigated by excision biopsy.
Malignant melanoma
Management
Complete excision is curative, local recurrence may oc- Definition
cur especially with morphoeic and superficial types. Ra- Malignant skin tumour, which arises from melanocytes
diotherapy can be used for large superficial carcinomas usually in the epidermis.
especially in older patients.
Incidence
Commonest skin cancer, rising in incidence.
Prognosis
Excision achieves a 95% cure with a recurrence rate of
Age
5% at 5 years.
Median age 50–55 years, rare in children.
Squamous cell carcinoma Geography
Particular problem in Caucasians.
Definition
A malignant tumour originating from squamous cells Aetiology
on the outer layer of the skin. Around 30% of melanomas arise from the junctional
component of a pre-existing naevus, which has become
Aetiology/pathophysiology dysplastic. Excess sun exposure, particularly a history
Sunlight and ionising radiation predispose to the devel- of childhood sunburn, is the major risk factor. Highest
opment epidermal dysplastic lesions: incidence in Caucasians with fair skin. Melanomas have