- Disease that is measurable. This is defined as lesions measuring at least 10mm on radiologic imaging. For lymph node disease, the lesion must measure at least 15 mm or have been biopsied and shown to contain melanoma. Skin or mucosal lesions that are not measurable on radiologic imaging but measure at least 10mm on clinical exam are also acceptable. (See Section 13.2 for detailed definition of measurable disease)