Blood and Other Tests 
• There are no blood tests available for screening or confirming the diagnosis of primary melanomas.
• Tumor-associated antigens shed by the tumor are now being looked at as possible markers in the bloodstream,
  but results are inconclusive. Carcinoembryonic antigen (CEA), which is found in several cancers, is not found in
  melanomas.

Endoscopy and Biopsy 
• An adequate—in other words, an excisional—biopsy is necessary for diagnosis. Examination of the tumor
  under the microscope reveals characteristic melanoma cells , which are typically plump and usually contain
  dustlike grains of melanin pigment. The malignant melanocytes are seen to migrate into the dermis to various
  depths, where they are found singly, in small groups or in large aggregations. Immunological staining procedures
  with special antibody-carrying dyes are now available to confirm the diagnosis in cases that do not appear
  typical.
• Shave biopsies are not recommended. They do not allow the depth of invasion into the skin to be determined,
  and this needs to be known to help predict whether the patient will be cured or has a risk of recurrence .
• Cauterization or freezing should never be done. These procedures destroy the superficial part of the melanoma,
  making diagnosis and staging impossible. They also leave tumor cells in deeper locations at the site, which
  could later give rise to seeding of other parts of the body.