Doctors diagnose skin cancer after an initial examination, a look at the patient's medical history, examination of skin patches and a biopsy of damaged skin cells, according to the American Cancer Society. Although a visual inspection of the site, known as a dermatoscopy, remains part of the initial investigation, doctors do not confirm a cancer diagnosis until after they see the results of a biopsy, notes the American Academy of Dermatology.
Doctors remove skin samples for biopsies using methods that vary by the type of cancer that the dermatologist suspects, states the American Cancer Society. A shave biopsy uses a scalpel to remove a thin layer of skin that may cause minor bleeding. A punch biopsy uses an instrument that looks like a cookie cutter and removes deeper layers of skin. A dermatologist may have to suture the wound from a punch biopsy. Fine needle aspirations could come into play if the skin cancer, or melanoma, spreads to other parts of the body, such as lymph nodes.
Once a doctor gets a sample, he sends the skin cells to a laboratory to get results, according to the American Cancer Society. Lab technicians perform three basic tests on the samples, and then doctors look at how fast cancer cells replicate and the thickness of the tumor. Cell division rates and tumor thickness help oncologists stage skin cancer so that they can determine a possible course of treatment.