Prognostic factors in malignant melanoma
Malignant melanoma is a relatively uncommon tumour in this country, but it accounts for most of the deaths attributable to skin cancer. Additionally, there is an established increasing incidence rate in every white population studied to date; it is therefore assuming greater importance. Despite the cutaneous location with the potential for early diagnosis, treatment and effective cure, the clinical behaviour of malignant melanoma still remains to a certain extent unpredictable. Today the Breslow measurement (thickness) of the tumour is regarded as the most sensitive prognostic indicator. Nonetheless, tumour thickness alone is not sufficient to predict the clinical outcome for the individual patient, with a 5-10% of 'thin' melanomas resulting in metastasis or death of the patient, and conversely it is recognised that a certain subgroup of 'thick' lesions will behave in a less aggressive than expected manner. Other features cited as influencing prognosis include patient age, sex, anatomical location, histogenetic type, mitotic counts, ulceration, vascular invasion, host response with a conflicting opinion on the role of regression. This thesis confirms the increasing incidence of melanoma in the Grampian Area, in keeping with other large studies and also that patients are presenting earlier with thin lesions. This thesis also confirms that some patients with thin melanomas develop metastasis and factors that may be important additional to the Breslow depth include lesion size, histological regression, Clark level and depth of the uninvolved dermis. Also, some thick melanomas do not metastasise and patients have a good disease free survival. Factors that appear to be important in this group of patients include anatomical location, vascular invasion and the nature of the lower tumour margin.