97 Skin Cancer—Melanoma
This chapter deals with the diagnosis and principles of management of cutaneous and mucosal melanoma of the head and neck.
97.1 Cutaneous Melanoma of the Head and Neck
Cutaneous melanoma is a malignant tumour of neural crest–derived cutaneous melanocytes. The incidence of melanoma is increasing rapidly and has done for the last few decades. It is caused by ultraviolet radiation (UVR) in susceptible individuals, especially if exposure occurs at a young age. Fair-skinned individuals, who burn easily in the sun, have fair or red hair and have a tendency to freckles are particularly vulnerable. The presence of atypical or dysplastic naevi and a family history (2%) are also relevant. A history of intense burning sun exposure of young unacclimatised white skin is the major risk factor for melanoma. This contrasts with the chronic sun damage which causes non-melanoma skin cancers.
Despite the increased incidence, the prognosis has improved. This improvement is mostly attributable to a higher proportion of thinner tumours because of earlier diagnosis and reflects the considerable effort expended in raising public and professional awareness of melanoma. Although melanoma is the major cause of skin cancer mortality, it is usually curable if treated at an early stage. In contrast, melanoma in its advanced stages is incurable.
Cutaneous melanoma is divided into sub-types based on clinical features and pathology:
• Superficial spreading melanoma.
• Nodular melanoma.
• Lentigo maligna melanoma (LMM).
• Acral lentiginous melanoma.
• Desmoplastic neurotropic melanoma.
97.1.1 Superficial Spreading Melanoma
This is the most frequently encountered type of melanoma. It is usually an asymmetrical pigmented lesion with irregular borders, pigmentation and outline. Patients may have noted growth, a change in sensation, colour, crusting, bleeding or inflammation of the lesion.
97.1.2 Nodular Melanoma
This usually has a shorter length of presentation and a greater tendency to bleeding and ulceration. It may occur both in sun-exposed and non-exposed areas of the skin. Clinically, it appears as a well-circumscribed blue/black lesion with areas of nodularity and involution within.
97.1.3 Lentigo Maligna Melanoma
This occurs most often in sun-damaged skin on the head and neck of older patients. It may be preceded by a pre-invasive (in situ) lesion called lentigo maligna (LM) before progressing in some instances to an invasive melanoma (LMM).
97.1.4 Acral Lentiginous Melanoma
The least common type of melanoma is the acral lentiginous melanoma. This may occur on the palms, soles and beneath the nails. It is more common in Afro-Caribbeans and Asians.
97.1.5 Desmoplastic Neurotropic Melanoma
This lesion is predominantly found in the head and neck. It has a greater propensity to local recurrence than other forms of melanoma, probably due to its tendency for perineural spread.
97.1.6 Clinical History
Do not concentrate on the lesion and forget it is attached to a patient. A history of sun exposure and involvement of any other risk factors should be documented. Avoidance advice should be supplemented with leaflets whenever possible. Document intercurrent diseases and the use of anticoagulant medication which will have implications for operative bleeding. Appropriate and safe arrangements for stopping these medications should be made (and the advice given in writing to the patients as they otherwise may forget).
The clinical diagnosis of melanoma can be difficult and various methods relating to the clinical history and examination findings have been suggested. Even then, the accuracy of diagnosis varies according to a clinician’s experience. Suspicious pigmented lesions are best examined in a good light with or without magnification and should be assessed using the seven-point checklist or ABCDE systems as given in Table 97.1 and Table 97.2.
Dermatoscopy is useful for diagnosis when used by those trained and experienced in the technique. Dermatoscopy refers to the examination of the skin using a handheld skin surface microscope. It is mainly used to evaluate pigmented lesions in order to distinguish melanoma and pigmented basal cell carcinoma, from benign melanocytic naevi and seborrhoeic keratoses. A high-quality lens giving 10 to 14 times magnification and a lighting system enables visualisation of sub-surface structures and patterns. With dermatoscopy, there is considerable improvement in the sensitivity (detection of melanomas) as well as specificity (percentage of non-melanomas correctly diagnosed as benign), compared with naked eye examination.
Examination of the cervical nodes is essential. It should be remembered that the nodes most often affected are those in the parotid gland, superficial jugular, upper deep cervical and occipital nodes. Lymphatic drainage is not always predictable and sentinel node biopsy using lymphoscintigraphy is a popular investigation for melanoma. Patients presenting with regional metastatic melanoma of unknown primary origin should be seen by a dermatologist for a skin examination, an ophthalmologist for examination of the eye and a head and neck surgeon for visualisation of the upper aerodigestive tract.