Tumor thickness is the most important variable in predicting the prognosis of a patient with a melanoma. Patients with thin lesions (a thickness less than 0.75 mm) have a 5-year survival rate greater than 98%. Patients with thick lesions (greater than 4 mm in thickness) have a 5-year survival rate less than 50%. The pathologist determines the thickness of the tumor and reports it in terms of the Breslow microstage (in millimeters) and the Clark level of invasion.
