Basal and Squamous Cell Skin Cancer Stages

The stage of a basal or squamous cell skin cancer is a description of how widespread the cancer is. This the most important factor in determining treatment and probable outcome.

For skin cancers, the stage is based on the cancer’s size and location, whether it has grown into nearby tissues or bones, whether it has spread to the lymph nodes or other parts of the body, and certain other factors.

Determining the stage of basal cell skin cancers is rarely needed, because these cancers are almost always cured before they spread to other parts of the body.

Squamous cell skin cancers are more likely to spread (although this risk is still small), so determining the stage can be more important, particularly in people who are at higher risk. This includes people with weakened immune systems, such as those who have had organ transplants and people infected with HIV, the virus that causes AIDS.

Staging is done using the tests and exams described in Tests for Basal and Squamous Cell Skin Cancers. In rare cases, imaging tests such as x-rays, CT scans, or MRI scans may be used as well.

Understanding your skin cancer stage

A staging system is a standard way to sum up how far a cancer has spread. This helps members of the cancer care team determine a patient’s prognosis (outlook) as well as the best treatment options.

The system most often used to stage basal and squamous cell skin cancers is the American Joint Commission on Cancer (AJCC) TNM system, which is based on 3 key pieces of information:

  • T stands for the main (primary) tumor (its size, location, and how far it has spread within the skin and to nearby tissues).
  • N stands for spread to nearby lymph nodes (bean-sized collections of immune system cells, to which cancers often spread first).
  • M is for metastasis (spread to other parts of the body).

T categories

TX: The main (primary) tumor cannot be assessed.

T0: No evidence of primary tumor.

Tis: Carcinoma in situ (the tumor is still just in the epidermis, the outermost skin layer).

T1: The tumor is 2 centimeters (cm) across (about 4/5 inch) or smaller and has no or only 1 high-risk feature (see below).

T2: The tumor is larger than 2 cm across, or is any size with 2 or more high-risk features.

T3: The tumor has grown into facial bones, such as the jaw bones or bones around the eye.

T4: The tumor has grown into other bones in the body or into the base of the skull.

High-risk features: These features are used to tell between some T1 and T2 tumors.

  • The tumor is thicker than 2 millimeters (mm).
  • The tumor has invaded down into the lower dermis or subcutis (Clark level IV or V).
  • The tumor has grown into tiny nerves in the skin (perineural invasion).
  • The tumor started on an ear or on a part of the lip.
  • The tumor cells look very abnormal (poorly differentiated or undifferentiated) under a microscope.

N categories

NX: Nearby lymph nodes cannot be assessed.

N0: The cancer has not spread to nearby lymph nodes.

N1: The cancer has spread to 1 nearby lymph node, which is on the same side of the body as the main tumor and is 3 centimeters (cm) or less across.

N2a: The cancer has spread to 1 nearby lymph node, which is on the same side of the body as the main tumor and is larger than 3 cm but not larger than 6 cm across.

N2b: The cancer has spread to more than 1 nearby lymph node on the same side of the body as the main tumor, none of which are larger than 6 cm across.

N2c: The cancer has spread to nearby lymph node(s) on the other side of the body from the main tumor, none of which are larger than 6 cm across.

N3: The cancer has spread to any nearby lymph node that is larger than 6 cm across.

M categories

M0: The cancer has not spread to other parts of the body.

M1: The cancer has spread to other parts of the body.

Stages of skin cancer

To assign an overall stage, the T, N, and M categories are combined. The stages are described using the number 0 and Roman numerals from I to IV. In general, people with lower stage cancers tend to have a better outlook for a cure or long-term survival.

Stage 0 Tis, N0, M0
Stage I T1, N0, M0
Stage II T2, N0, M0
Stage III T3, N0, M0
T1 to T3, N1, M0
Stage IV T1 to T3, N2, M0
Any T, N3, M0
T4, any N, M0
Any T, any N, M1


The American Cancer Society medical and editorial content team
Our team is made up of doctors and master’s-prepared nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

Source: Basal and Squamous Cell Skin Cancer Stages