Skin Cancer Stages

Many types of skin cancer have their own stages. These include melanoma skin cancer and Merkel cell carcinoma. 

Basal cell carcinoma of the skin and squamous cell carcinoma of the skin share staging systems when they appear on the head and neck. There are no stages for these cancers when they start on other parts of the body. 

Source: National Cancer Institute

Stage 0 (Carcinoma in situ)

In stage 0, abnormal cells are found in the squamous cell or basal cell layer of the epidermis. These abnormal cells may become cancer and spread into nearby normal tissue. Stage 0 is also called carcinoma in situ.

Stage I

In stage I, cancer has formed and the tumor is 2 centimeters or smaller.

Stage II

In stage II, the tumor is larger than 2 centimeters but not larger than 4 centimeters.

Stage III

In stage III, one of the following is found:

• the tumor is larger than 4 centimeters, or cancer has spread to tissue covering the nerves below the dermis, or has spread below the subcutaneous tissue, or has spread to the bone and the bone has minor damage. Cancer may have also spread to one lymph node on the same side of the body as the tumor and the node is 3 centimeters or smaller, and cancer has not spread through to the outside covering of the lymph node; or
• the tumor is 4 centimeters or smaller. Cancer has spread to one lymph node on the same side of the body as the tumor and the node is 3 centimeters or smaller.

Stage IV

In stage IV, one of the following is found:

• the tumor is any size and cancer may have spread to the bone and the bone has minor damage, or to tissue covering the nerves below the dermis, or below the subcutaneous tissue. Cancer has spread to the lymph nodes as follows:
  • one lymph node on the same side of the body as the tumor, the affected node is 3 centimeters or smaller, and cancer has spread through to the outside covering of the lymph node; or
  • one lymph node on the same side of the body as the tumor, the affected node is larger than 3 centimeters but not larger than 6 centimeters, and cancer has not spread through to the outside covering of the lymph node; or
  • more than one lymph node on the same side of the body as the tumor, the affected nodes are 6 centimeters or smaller, and cancer has not spread through to the outside covering of the lymph nodes; or
  • one or more lymph nodes on the opposite side of the body as the tumor or on both sides of the body, the affected nodes are 6 centimeters or smaller, and cancer has not spread through to the outside covering of the lymph nodes.
• the tumor is any size and cancer may have spread to tissue covering the nerves below the dermis, or below the subcutaneous tissue, or to bone marrow or to bone, including the bottom of the skull. Also:
  • cancer has spread to one lymph node that is larger than 6 centimeters and cancer has not spread through to the outside covering of the lymph node; or
  • cancer has spread to one lymph node on the same side of the body as the tumor, the affected node is larger than 3 centimeters, and cancer has spread through to the outside covering of the lymph node; or
  • cancer has spread to one lymph node on the opposite side of the body as the tumor, the affected node is any size, and cancer has spread through to the outside covering of the lymph node; or
  • cancer has spread to more than one lymph node on one or both sides of the body and cancer has spread through to the outside covering of the lymph nodes.
• the tumor is any size and cancer has spread to bone marrow or to bone, including the bottom of the skull, and the bone has been damaged. Cancer may have also spread to the lymph nodes; or
• cancer has spread to other parts of the body, such as the lung.

Source: National Cancer Institute

Stage 0 (Carcinoma in situ)

In stage 0, abnormal cells are found in the epidermis, usually in the basal cell layer. These abnormal cells may become cancer and spread into nearby normal tissue. Stage 0 is also called carcinoma in situ.

Stage I

In stage I, cancer has formed. Stage I is divided into stages IA and IB.

• Stage IA: The tumor is 10 millimeters or smaller and may have spread to the edge of the eyelid where the lashes are, to the connective tissue in the eyelid, or to the full thickness of the eyelid.
• Stage IB: The tumor is larger than 10 millimeters but not larger than 20 millimeters and the tumor has not spread to the edge of the eyelid where the lashes are, or to the connective tissue in the eyelid.

Stage II

Stage II is divided into stages IIA and IIB.

• In stage IIA, one of the following is found:
  • the tumor is larger than 10 millimeters but not larger than 20 millimeters and has spread to the edge of the eyelid where the lashes are, to the connective tissue in the eyelid, or to the full thickness of the eyelid; or
  • the tumor is larger than 20 millimeters but not larger than 30 millimeters and may have spread to the edge of the eyelid where the lashes are, to the connective tissue in the eyelid, or to the full thickness of the eyelid.
• In stage IIB, the tumor may be any size and has spread to the eye, eye socket, sinuses, tear ducts, or brain, or to the tissues that support the eye.

Stage III

Stage III is divided into stages IIIA and IIIB.

• Stage IIIA: The tumor may be any size and may have spread to the edge of the eyelid where the lashes are, to the connective tissue in the eyelid, or to the full thickness of the eyelid, or to the eye, eye socket, sinuses, tear ducts, or brain, or to the tissues that support the eye. Cancer has spread to one lymph node on the same side of the body as the tumor and the node is 3 centimeters or smaller.
• Stage IIIB: The tumor may be any size and may have spread to the edge of the eyelid where the lashes are, to the connective tissue in the eyelid, or to the full thickness of the eyelid, or to the eye, eye socket, sinuses, tear ducts, or brain, or to the tissues that support the eye. Cancer has spread to lymph nodes as follows:
  • one lymph node on the same side of the body as the tumor and the node is larger than 3 centimeters; or
  • more than one lymph node on the opposite side of the body as the tumor or on both sides of the body.

Stage IV

In stage IV, the tumor has spread to other parts of the body, such as the lung or liver.

Source: National Cancer Institute

Stage 0 melanoma (melanoma in situ)

In stage 0, abnormal melanocytes are found in the epidermis. These abnormal melanocytes may become cancer and spread into nearby normal tissue. Stage 0 is also called melanoma in situ.

Stage I melanoma

In stage I, cancer has formed. Stage I is divided into stages IA and IB.

Stage IA: The tumor is not more than 1 millimeter thick, with or without ulceration.

Stage IB: The tumor is more than 1 but not more than 2 millimeters thick, without ulceration.

Stage II melanoma

Stage II is divided into stages IIA, IIB, and IIC.

Stage IIA: The tumor is either:

• more than 1 but not more than 2 millimeters thick, with ulceration; or
• more than 2 but not more than 4 millimeters thick, without ulceration.

Stage IIB: The tumor is either:

• more than 2 but not more than 4 millimeters thick, with ulceration; or
• more than 4 millimeters thick, without ulceration.

Stage IIC: The tumor is more than 4 millimeters thick, with ulceration.

Stage III melanoma

Stage III is divided into stages IIIA, IIIB, IIIC, and IIID.

Stage IIIA: The tumor is not more than 1 millimeter thick, with ulceration, or not more than 2 millimeters thick, without ulceration. Cancer is found in 1 to 3 lymph nodes by sentinel lymph node biopsy.

Stage IIIB:

• (1) It is not known where the cancer began or the primary tumor can no longer be seen, and one of the following is true:
  • cancer is found in 1 lymph node by physical exam or imaging tests; or
  • there are microsatellite tumors, satellite tumors, and/or in-transit metastases on or under the skin.

or

• (2) The tumor is not more than 1 millimeter thick, with ulceration, or not more than 2 millimeters thick, without ulceration, and one of the following is true:
  • cancer is found in 1 to 3 lymph nodes by physical exam or imaging tests; or
  • there are microsatellite tumors, satellite tumors, and/or in-transit metastases on or under the skin.

or

• (3) The tumor is more than 1 but not more than 2 millimeters thick, with ulceration, or more than 2 but not more than 4 millimeters thick, without ulceration, and one of the following is true:
  • cancer is found in 1 to 3 lymph nodes; or
  • there are microsatellite tumors, satellite tumors, and/or in-transit metastases on or under the skin.

Stage IIIC:

• (1) It is not known where the cancer began, or the primary tumor can no longer be seen. Cancer is found:
• in 2 or 3 lymph nodes; or
• in 1 lymph node and there are microsatellite tumors, satellite tumors, and/or in-transit metastases on or under the skin; or
• in 4 or more lymph nodes, or in any lymph nodes that are matted together; or
• in 2 or more lymph nodes and/or in any lymph nodes that are matted together. There are microsatellite tumors, satellite tumors, and/or in-transit metastases on or under the skin.

or

• (2) The tumor is not more than 2 millimeters thick, with or without ulceration, or not more than 4 millimeters thick, without ulceration. Cancer is found:
• in 1 lymph node and there are microsatellite tumors, satellite tumors, and/or in-transit metastases on or under the skin; or
• in 4 or more lymph nodes, or in any lymph nodes that are matted together; or
• in 2 or more lymph nodes and/or in any lymph nodes that are matted together. There are microsatellite tumors, satellite tumors, and/or in-transit metastases on or under the skin.

or

• (3) The tumor is more than 2 but not more than 4 millimeters thick, with ulceration, or more than 4 millimeters thick, without ulceration. Cancer is found in 1 or more lymph nodes and/or in any lymph nodes that are matted together. There may be microsatellite tumors, satellite tumors, and/or in-transit metastases on or under the skin.

or

• (4) The tumor is more than 4 millimeters thick, with ulceration. Cancer is found in 1 or more lymph nodes and/or there are microsatellite tumors, satellite tumors, and/or in-transit metastases on or under the skin.

Stage IIID: The tumor is more than 4 millimeters thick, with ulceration. Cancer is found:

• in 4 or more lymph nodes, or in any lymph nodes that are matted together; or
• in 2 or more lymph nodes and/or in any lymph nodes that are matted together. There are microsatellite tumors, satellite tumors, and/or in-transit metastases on or under the skin.

Stage IV melanoma

In stage IV, the cancer has spread to other parts of the body, such as the lung, liver, brain, spinal cord, bone, soft tissue (including muscle), digestive tract, and/or distant lymph nodes. Cancer may have spread to places in the skin far away from where it first started.

Source: National Cancer Institute

Stage 0  Merkel cell carcinoma (carcinoma in situ)

In stage 0, abnormal Merkel cells are found in the top layer of skin. These abnormal cells may become cancer and spread into nearby normal tissue.

Stage I Merkel cell carcinoma 

In stage I, the tumor is two centimeters or smaller.

Stage II Merkel cell carcinoma

Stage II Merkel cell carcinoma is divided into stages IIA and IIB.

• In stage IIA, the tumor is larger than two centimeters.
• In stage IIB, the tumor has spread to nearby connective tissue, muscle, cartilage, or bone.

Stage III Merkel cell carcinoma

Stage III Merkel cell carcinoma is divided into stages IIIA and IIIB.

In stage IIIA, either of the following is found:

• the tumor may be any size and may have spread to nearby connective tissue, muscle, cartilage, or bone. A lymph node cannot be felt during a physical exam but cancer is found in the lymph node by sentinel lymph node biopsy or after the lymph node is removed and checked under a microscope for signs of cancer; or
• a swollen lymph node is felt during a physical exam and/or seen on an imaging test. When the lymph node is removed and checked under a microscope for signs of cancer, cancer is found in the lymph node. The place where the cancer began is not known.

In stage IIIB, the tumor may be any size and:

• may have spread to nearby connective tissue, muscle, cartilage, or bone. A swollen lymph node is felt during a physical exam and/or seen on an imaging test. When the lymph node is removed and checked under a microscope for signs of cancer, cancer is found in the lymph node; 
• or cancer is in a lymph vessel between the primary tumor and lymph nodes that are near or far away. Cancer may have spread to lymph nodes.

Stage IV Merkel cell carcinoma

In stage IV, the tumor has spread to skin that is not close to the primary tumor or to other parts of the body, such as the liver, lung, bone, or brain.