Clinical and Histologic Features of Level 2 Cutaneous Malignant Melanoma Associated with Metastasis

BACKGROUND, Metastatic melanoma developing in patients with a level 2 primary cutaneous malignant melanoma (CMM) is rare but has been reported in studies with follow-up periods ranging up to 15 years. The objective of this study was to investigate level 2 CMM associated with metastasis in a population-based retrospective study. METHODS, In this retrospective population-based study, all level 2 CMMs associated with metastases were identified in Western Australia during 1982-1989 and were followed up to the end of 1996. RESULTS. Pathology reports of 2834 patients were examined. Of these, 1716 had a CMM of maximum rumor thickness 1 mm or less recorded on the pathology report. Of these, 67 had a metastatic melanoma reported on follow-up, Histologic review of these 67 cases under blind conditions identified 5 cases with a level 2 primary CMM followed by metastasis without another primary CMM. All these level 2 CMM showed established regression. Eight other patients were identified with a level 2 CMM, metastatic melanoma, and another primary CMM of at least level 3 invasion. These subsequent primaries occurred before the metastasis had been reported. CONCLUSIONS, These findings suggest that metastasis from level 2 CMM without regression is very rare, if it occurs at all. (C) 2001 American Cancer Society.