The Natural Break Points for Primary-Tumor Thickness in Clinical Stage I Melanoma

To the Editor: Thickness of the primary tumor in millimeters is currently the best prognostic factor for patients with clinical Stage I melanoma, 1 2 3 4 5 6 7 even if regional lymph nodes contain metastases. 1 However, the mortality rate does not increase in a nearly perfect linear fashion with thickness, as assumed by investigators who have reported survival rates and used regular thickness increments. 5 6 7 Instead, the risk increases with thickness in quantum jumps, analogous to a rising staircase, with four "stair steps" or categories with the following boundaries: 3.60 mm. The respective . . .