Nonmelanoma Skin Cancer Staging

Skin cancers can begin as small localized lesions and in some cases may grow to affect larger areas of skin. Skin cancer can spread across the skin’s surface, and down into the skin’s deeper layers. Staging is the process by which a tumor is assigned a severity rating, based on a number of factors. Prognosis and treatment options often depend on the stages of skin cancer.

Skin cancer generally falls into one of two categories: melanoma skin cancer and nonmelanoma skin cancer (including both squamous cell carcinoma and basal cell carcinoma).

The American Joint Commission on Cancer (AJCC) TNM System

The AJCC TNM staging system is the current preferred method for melanoma and nonmelanoma skin cancer staging. This system uses three parameters to classify skin cancer:

  • T stands for tumor. The tumor is assigned a number from zero to four based on its size (how much of the skin’s surface is covered by the tumor). Other factors are also considered when assigning a T value, including how far it penetrates down into the skin, the rate of cell division and the appearance and location of the tumor and cancerous cells.
  • N stands for the lymph nodes, part of the body’s immune system. A number from zero to three is assigned based on the degree to which cancer cells have spread to the lymph nodes.
  • M stands for metastasis, the process in which secondary tumors grow in distant parts of the body after cells break off from the original tumor and travel to other body parts.

Among nonmelanoma skin cancers, the TNM system is most often used for squamous cell carcinoma. Basal cell carcinoma is less likely to spread to other areas of the body, so TNM stages of cancer may not always be assigned. However, basal cell lesions can be described in terms of both horizontal and vertical size. Merkel cell carcinoma, a rare non-melanoma skin cancer, has its own AJCC staging system.

The TNM staging system allows for highly specific classifications of skin cancer lesions. These components are considered together when determining a stage from 0-4:

  • Stage 0 (carcinoma in situ): A precancerous lesion is present.
  • Stage 1: The lesion is less than two centimeters wide.
  • Stage 2: The lesion is greater than two centimeters wide.
  • Stage 3: Cancer has spread to the lymph nodes or nearby skin tissue.
  • Stage 4: Cancer has metastasized to distant organs.

Precancerous Skin Lesions

In some cases, a precancerous lesion, such as an actinic keratosis, can be found on the skin. These lesions are often removed, because they may eventually develop into squamous cell carcinoma. Actinic keratoses are considered to be stage 0 skin cancers, also called carcinoma in situ.

Skin cancer identified as a precancerous lesion, or in an early stage of progression, is more responsive to skin cancer treatment, and poses less of a threat than cancer that remains undiscovered until after it has reached an advanced stage.

Resources

American Cancer Society. (2010). How is basal and squamous cell skin cancer staged? Retrieved June 30, 2010, from http://our.cancer.org/docroot/CRI/content/CRI_2_4_3X_How_is_skin_cancer_staged_51.asp

American Cancer Society. (2010). Skin cancer: Basal and squamous cell. Retrieved June 30, 2010, from http://www.cancer.org/acs/groups/cid/documents/webcontent/003139-pdf.pdf

National Cancer Institute. (2010). Skin cancer treatment (PDQ). Retrieved June 30, 2010, from http://www.cancer.gov/cancertopics/pdq/treatment/skin/Patient/page2#Keypoint8