Incidence of locally metastatic ('recurrent') cutaneous malignant melanoma following conventional wide margin excisional surgery for invasive clinical stage I tumours: importance of maximal primary tumour thickness.

In a minimum 5-year follow-up study of 638 primary clinical Stage I invasive cutaneous malignant melanomas (excluding lentigo maligna melanomas) excised with conventional wide normal tissue margins, the incidence of local tumour metastasis was 48/638 (8 per cent). The incidence of locally metastatic tumours rose from 2 per cent for tumours less than 0.99 mm thick, to 14 per cent for tumours between 5 and 6 mm in thickness. The rate of local metastasis was significantly greater for tumours greater than 2.0 mm compared with tumours less than 2.0 mm thick (P less than 0.01). Despite the anatomical restrictions to wide resection margins in the head and neck, these areas had the lowest regional incidence for local tumour metastasis (2 per cent). Over the prolonged postoperative follow-up period (median 11 years) 67 per cent (32/48) of patients with locally metastatic disease died of disseminated malignant melanoma, compared with a 31 per cent mortality (180/590) for those without local disease metastasis. The term 'local recurrence' is unhelpful in our attempts to understand the pathology of malignant melanoma, and the term 'local metastasis' could replace it with benefit.