Staging of Basal Cell Carcinoma and Squamous Cell Carcinoma

Basal cell carcinoma often is not "staged" like other cancers, because it rarely invades distant organs or sites. Exceptions are made in cases of very large or widespread basal cell cancers. It is also uncommon for squamous cell carcinoma to be staged, although the risk of cancer metastasis is slightly greater for this type of cancer. If staging is necessary, the most widely used method is the TNM system. This classification scheme is used to describe the size (T), lymph node involvement (N), and/or metastasis (M) of the tumor.

The primary tumor (T) is classified according to the following categories:

  • TX: The primary tumor cannot be assessed.
  • T0: There is no evidence of primary tumor.
  • T1: Tumor is 2 centimeters or less in greatest dimension.
  • T2: Tumor is more than 2 centimeters, but less than 5 centimeters in greatest dimension.
  • T3: Tumor is more than 5 centimeters in greatest dimension.
  • T4: Tumor invades the deep, extradermal structures (cartilage, bone, or muscle).

The regional lymph nodes (N) are clinically divided into the following categories:

  • NX: Regional (nearby) lymph nodes cannot be assessed.
  • N0: There is no regional lymph node metastasis.
  • N1: Regional lymph node metastasis is present.

The state of metastasis (M) is defined as follows:

  • MX: Distant metastasis cannot be assessed.
  • M0: There is no distant metastasis.
  • M1: Distant metastasis is present.

There are four basic stage groupings within the TNM system, as well as a "Stage 0" classification, which refers to carcinoma in situ:

  • Stage 0: Tis, N0, M0
  • Stage 1: T1, N0, M0; or
  • Stage 2: T2, N0, M0; or T3, N0, M0
  • Stage 3: T4, N0, M0; or T(any), N1, M0
  • Stage 4: T(any), N(any), M1

In general, people have a better prognosis (disease outcome) and hope of cure if they have low- versus high-stage tumors. It is important to remember that staging is based on information from groups of patients, and it may not reflect cancer behavior in a particular individual.

Clinical Staging of Skin Cancer

The clinical staging of basal cell or squamous cell carcinoma can be simplified as follows:

Stage 0: Carcinoma in situ that is confined to the epidermis - the top layer of the skin (see Skin Anatomy). Squamous cell carcinoma in situ - also known as Bowen's disease - is the first stage of squamous cell skin cancer.
Stage 1: Small tumor that is less than 2 centimeters in size and has not spread to the lymph nodes or other organs.
Stage 2: Tumor that is larger than 2 centimeters, but has not spread to the lymph nodes or other organs.
Stage 3: Tumor that has metastasized (spread) to the tissues under the skin (muscle, bone, or cartilage) and/or to the regional (nearby) lymph nodes.
Stage 4: Tumor of any size that has metastasized (spread) to distant organs such as the lungs or brain.

Publication Review By: the Editorial Staff at

Published: 15 Aug 1999

Last Modified: 26 Feb 2015