What Are the Stages of Non-Melanoma Skin Cancer?

Staging of a cancer provides a way to describe a tumor and whether and how far it has spread. The higher the stage number, the more widespread is the cancer. These stages are used to determine the type of treatment for non-melanoma skin cancer.

A staging system has been developed for basal and squamous cell carcinomas, the most common types of skin cancer. There is also a staging system for Merkel cell carcinoma. The rarity of other types of non-melanoma skin cancer makes it difficult to devise a staging system for these cancers.

The TNM System

Once a biopsy has been performed, a tool called the TNM (tumor, node, metastasis) system can be used to determine the stage of non-melanoma. This system is not a staging system in itself; rather, it is used to define the characteristics of the tumor so that the stage can then be determined.

The TNM system uses three criteria. The first is the size of the tumor itself (T). The second indicates the number of lymph nodes (N) involved. (The lymph system helps drain fluid and waste from the body, and lymph nodes are like tiny way stations that filter out impurities and help fight infection.) The third criterion is metastasis (M), or whether and how far the cancer has spread to other areas of the body. The results of these three criteria are combined to determine the stage of cancer.

In the TNM system for non-melanoma skin cancer, the “T” indicates the thickness of the tumor:

The “N” in the TNM staging system indicates whether and how the regional lymph nodes have been affected by the cancer:

The “M” in the TNM system refers to distant metastases—whether, and how far, the cancer has spread outside the original site:

Staging of Basal and Squamous Cell Carcinomas

The stages of basal and squamous cell cancers are determined according to the TNM system:

American Joint Committee on Cancer (AJCC) Staging System for Basal and Squamous Cell Carcinomas
Stage	TNM	Characteristics
Stage 0	Tis N0 M0	The cancer involves only the epidermis and has not spread to the dermis. Squamous cell carcinoma in situ is also called Bowen’s disease.
Stage I	T1 N0 M0	The cancer is no larger than 2 centimeters (between three-quarters and  seven-eighths inch). It has not invaded into muscle, cartilage, or bone and has not spread to lymph nodes or other organs.
Stage II	T2      T3 N0 or N0 M0     M0	The cancer is larger than 2 centimeters and has not invaded into muscle, cartilage, or bone and has not spread to lymph nodes or other organs.
Stage III	T4     AnyT N0 or N1 M0     M0	The cancer has grown into tissues beneath the skin (such as muscle, bone, or cartilage) and/or it has spread to regional (nearby) lymph nodes. In this stage, the cancer has not spread to other organs such as the lungs or brain.
Stage IV	Any T Any N M1	The cancer can be any size and may or may not have spread to local lymph nodes. It has spread to other organs, such as the lungs or brain.

Staging of Merkel Cell Carcinoma

• Stage I - The cancer has not spread to lymph nodes or other parts of the body.
• Stage II - The cancer has spread to nearby lymph nodes, but not to other parts of the body.
• Stage III - The cancer has spread beyond the nearby lymph nodes and to other parts of the body.
• Recurrent - The cancer has recurred after treatment, either in the same location or in another part of the body.

This content has been reviewed and approved by Myo Thant, MD.