The object of this study was to evaluate the prognostic impact of a cross-sectional area measured in routinely stained slides of cutaneous melanoma using fully automated image analysis. Hematoxylin-eosin stained slides of 238 specimens of primary cutaneous melanoma with Clark levels III to V were evaluated by digital image analysis using color video images, a scanning stage, and autofocus equipment. The cross-sectional area was significantly related to metastasis-free survival. Lesions with a cross-sectional area < or = 12 mm2 showed a 2-year metastasis-free survival rate of 92+/-2% compared with 41+/-8% in lesions with a cross-sectional area > 12 mm2 (log rank test: z = 71, p < 0.0001). The same was true for overall survival (98+/-1% compared with 82+/-6%; z = 42.12, p < 0.0001). In multivariate analysis, the cross-sectional area seems to provide prognostic information in addition to that provided by Breslow's index. In cases with regression and in small melanomas with vertical growth, however, metastatic spread may occur in lesions with a small cross-sectional area. It was concluded that automated measurement of the cross-sectional area may be helpful in assessing prognosis in cutaneous melanoma.