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Histological characteristics of metastasizing thin melanomas: a case-control study of 43 cases
Joan Guitart1, Lori Lowe, Michael Piepkorn
1Department of Dermatology, Northwestern University Medical School, 675 N St Clair, Suite 19-150, Chicago, IL 60611, USA. j-guitart@nwu.edu
Objective:
To study clinical and histological features associated with metastasizing thin melanomas (MTMs).
Design:
Case-control study of clinicopathological features of patients with MTMs by a panel of 10 dermatopathologists.
Setting:
Members of the North American Melanoma Pathology Study Group selected the cases from the melanoma databases at 8 academic institutions.
Patients:
Forty-three patients with MTMs (<1 mm thick) and 42 control subjects without metastasis matched for age, sex, tumor site, and Breslow thickness.
Intervention:
None.
Main Outcome Measures:
Clinical (age, sex, site of lesion, stage at diagnosis, metastasis site, disease-free survival, and outcome) and histological (Breslow thickness, Clark level, growth phase, regression, and inflammatory response) features of patients with MTMs vs controls.
Results:
There was an overrepresentation of axial tumors among patients with MTMs. Extensive regression was present in 18 patients (42%) with MTM vs 2 matched control subjects (5%) (95% confidence interval, 21%-53%; P =.001). Other histological variables were not significantly different. Two patients had melanomas in situ with subsequent metastasis.
Conclusions:
Thin melanomas with extensive regression represent a group at higher risk for the development of metastasis. Furthermore, the risk of metastasis cannot be dismissed in cases of melanoma in situ.