- Have measurable disease in their skin by direct visualization (visible lesion typically > 0.5 cm in maximal diameter); to perform a microscopic observation, the lesion will have to be visible by the naked eye, lined-up visually, and be able to interface with the microscope objective; a melanoma lesion that is smaller than 0.5 cm in diameter would present several obstacles to obtaining a reliable microscopic observation in the operating room; therefore, a visible lesion, at a minimum of 0.5 cm in diameter, is proposed for this study