Diagnosing Skin Cancer

Skin cancer is usually found by observation of a change in the skin’s appearance. Once an abnormal growth has been found, the diagnosis of cancer is made by examining the cells of the lesion. This helps to determine whether abnormal cancer cells are present, and if so, what type of cancer they represent.

Finding Skin Cancer

The first step in diagnosing skin cancer is identifying lesions that may be malignant. Skin cancer is found by observing the skin for changes, including new abnormal growths, or changes to existing moles. Suspicious cancerous or precancerous lesions can be found through a skin check by a doctor, or with a self-check of your skin.

Keep in mind the ABCDE rule when examining your skin for potentially cancerous lesions:

  • A is for asymmetry: Uneven and oddly shaped
  • B is for borders: Ragged or irregular outline
  • C is for color: Several colors in one mole
  • D is for diameter: Larger than a pencil eraser
  • E is for evolving: Changing appearance over time.

Confirming the Diagnosis

When a potentially cancerous mole is found, your doctor will most often perform a skin biopsy. This is a surgical procedure in which a sample consisting of all or part of the skin lesion is removed, so it can be examined in more detail. The tissue is examined under a microscope to determine if abnormal cancerous cells are present. Common types of biopsy for skin cancer include:

  • Excisional biopsy: The entire lesion is removed with a scalpel.
  • Punch biopsy: A round, hollow blade is used to remove a cylinder of skin.
  • Shave biopsy: A sharp blade is used to shave off the lesion.

Other types of biopsies may be needed for advanced skin cancer that may have spread to other organs or lymph nodes.

If cancerous cells are found, the doctor may go back to perform further testing in the lesion. This can help to determine the stage of the cancer. Staging is a process used to describe the size and extent of a lesion, including how large an area of skin is covered and how deeply the lesion penetrates the skin. Cancer staging helps to establish prognosis; cancers found and treated at a more advanced stage tend to have a poorer outlook.

The Importance of Early Diagnosis

Early diagnosis is crucial for favorable prognosis in skin cancer. Even for the deadliest skin cancer, melanoma, diagnosis in the earliest stages makes the cancer highly treatable. It is therefore important to familiarize yourself with your skin’s appearance, and check it often for changes or new growths. This is particularly true if you have certain risk factors, such as a family history of skin cancer, a history of long-term sun exposure or very fair skin.

If you see something suspicious, tell your doctor, who can help you with the next steps of diagnosis, as well as skin cancer treatment options.


American Academy of Family Physicians. (2009.). Skin cancer: Saving your skin from sun damage. Retrieved June 29, 2010, from

National Cancer Institute. (2010). General information about skin cancer. Retrieved June 29, 2010, from http://www.cancer.gov/cancertopics/pdq/treatment/skin/Patient

Portland Dermatology Clinic. (n.d.). What is skin cancer? Retrieved June 29, 2010, from http://portlanddermclinic.com/index.php?page=What is Skin Cancer?