IN THIS issue of the ARCHIVES, the members of the North American Melanoma Pathology Study Group report on the histological characteristics of thin metastasizing melanomas.1 The North American Melanoma Pathology Study Group is composed of pathologists from the United States and Canada; this group meets twice a year to review specific issues in regard to the pathological aspect of pigmented lesions and melanoma. Their study showed that thin melanomas with extensive regression represented a group at higher risk for metastasis. The investigators searched electronic records from melanoma databases and pathology departments at 8 academic centers and identified 43 patients with a melanoma smaller than 1.0 mm and a known history of metastases. All the metastases were confirmed by histological examinations. From each melanoma case, representative slides were independently reviewed by a panel of 10 dermatopathologists experienced in pigmented lesions. The control group included 42 patients with thin melanomas, with no evidence of metastases after a minimum of follow-up of 6 years. The controls were matched for sex, age, tumor site, and Breslow thickness. For all control cases, the diagnosis of melanoma was confirmed. The main outcome measures were clinical and histological features of thin metastasizing melanomas compared with control. The investigators demonstrated that there was an overrepresentation of axial tumors among patients with thin metastasizing melanomas. Extensive regression was present in 42% of patients with thin metastasizing melanomas compared with 5% of the matched controlled cases (difference, 37%; 95% confidence interval [CI], 21%-53%; P = .001). Of note, 2 patients had in situ melanoma, which subsequently metastasized. The investigators concluded that thin melanomas with extensive spontaneous regression are a group with higher potential for metastases, particularly if the primary lesion involved the torso.
Demierre M. Thin Melanomas and Regression, Thick Melanomas and Older MenPrognostic Implications and Perspectives on Secondary Prevention. Arch Dermatol. 2002;138(5):678-682. doi:10.1001/archderm.138.5.678