[Longitudinal study of different metastatic patterns in the progression of cutaneous melanoma]

Compared with other tumors, melanoma has displayed one of the largest increases in incidence in recent years, and it is known to have a high metastatic potential. In cases of metastasis, approximately two-thirds of patients have lymph-node metastases and one-third develop systemic metastases. However, few studies have been reported that analyzed different metastatic patterns according to the natural history of melanoma. The main aim of this study was to analyze the different metastatic pathways and patterns and to assess the time course of development of metastases from cutaneous melanoma.

A retrospective study was performed in 575 patients with onset of primary melanoma between 1990 and 2004. During follow-up, 67 patients developed metastases. Different pathways for metastasis were established and evaluated. We identified 4 metastatic pathways according to the metastatic pattern during progression of the melanoma. The time course of metastases was also evaluated. Finally, we analyzed melanomas with local recurrence in terms of whether or not systemic progression occurred.

Melanoma metastases first occurred in local lymph nodes in 55.2 % of the patients. Initial metastasis was systemic in 14.9 % of the patients. The anatomical location and tumor thickness influenced which metastatic pathway was followed. Distant metastases occurred after a mean of 25 months regardless of the pathway followed

The development of distant metastases displays a constant time course and the time to onset is independent of the metastatic pathway. This observation may explain why sentinel lymph node biopsy has a limited impact on overall survival of melanoma patients.