Local recurrence of melanoma.

Local recurrence (LR) of cutaneous malignant melanoma (CMM) is a controversial issue, especially in regard to recommendations for margins of excision of primary CMM. Factual evidence in support of the belief that wider margins of excision decrease the risk of local recurrence is meagre, but recommendations for adjusting margins of excision according to tumour thickness are still presented. The histological features of LR indicate that two mechanisms are involved: (1) persistent growth of incompletely excised primary melanoma, and (2) local metastasis. The second group comprises the most common form of LR and is associated with a poor prognosis, indicating that it is a manifestation of systemic disease. The morphological features and the prognostic implications of LR indicate that many are due to haematogenous rather than lymphatic metastasis alone and, therefore, are not preventable by wider excisions beyond complete excision of the primary tumour itself. The concept that most LRs are metastases is consistent with the failure of wide margins of excision to prevent LR. The higher risk of LR associated with greater tumour thickness is associated with the increased risk of metastasis from the thicker tumours, not with the extent of excision. The resolution of the controversy regarding the primary surgical treatment of CMM depends on the recognition by pathologists and clinicians alike that the two types of LR have diagnostic microscopic features and that they have entirely different implications for prognosis.