Diagnosis of Skin Cancer of the Feet

Diagnosis of melanoma often begins when a person notices a skin change during a simple self-examination. Many physicians suggest a monthly self-exam, especially in individuals who have a previous history of skin cancer.

Skin Self-examination

  • After a bath or shower, examine your skin in a bright room that has a full-length mirror. A hand-held mirror will help you see the front, back, and sides (including the underarms and backs of the legs and feet), as well as the skin between the buttocks, the genital area, soles of the feet, spaces between the toes, and the scalp (a blow dryer can help to move the hair away from the scalp for easier viewing).
  • Note the location, size, shape, number, and color of all familiar moles, birthmarks, scars, and blemishes.
  • Record any new or unusual changes in the skin such as a sore that does not heal, or a mole that has grown or changed color.
  • If you notice any changes, consult a physician as soon as possible.

Many types of skin cancer, including malignant melanomas, can resemble common moles. Melanoma worsens as it expands into the deeper layers of the skin and once it reaches the dermis, it can enter the blood vessels and spread (metastasize) to other parts of the body. The depth of the melanoma is the most important factor in determining the expected disease outcome (prognosis). The depth of penetration determines the stage of the disease.

The stage of the cancer indicates the extent of disease and the proper treatment. The stage of melanoma is determined by the depth of the lesion into the skin, and whether it has spread. The thickness and depth of the tumor are measured with a device that is used to measure small distances when looking through a microscope (called an ocular micrometer). The thickness of the melanoma is used to stage the disease according to the American Joint Committee on Cancer (AJCC) staging system. Another staging system, the Clark method, bases staging on the level of invasion, or which tissues the tumor has penetrated (i.e., which skin layer). It is generally believed that the thickness of the tumor is more accurate than the level of invasion for choosing an appropriate treatment.

AJCC Staging System

The AJCC staging system is based on three sets of criteria: thickness of the tumor (T), extent to which it has spread to the lymph nodes (N), and extent to which it has metastasized to other parts of the body (M). The AJCC staging system is outlined below, with the TNM parameters and corresponding Clark method stage in parentheses. The TNM levels are explained following the outline of the staging system. When the AJCC and the Clark method stages do not correspond, the AJCC system takes precedence.

Stage 0

This is melanoma in situ, meaning the cancer is in the epidermis and has not begun to spread yet. (Clark's level I)

Stage IA

Localized melanoma that is less than 0.75 mm (Clark's level II: the tumor has spread to the upper dermis; T1N0M0).

Stage IB

Localized melanoma that is thicker than 0.75 mm but less than 1.5 mm (Clark's level III: the tumor involves most of the upper dermis); T2N0M0).

Stage IIA

Localized melanoma that is thicker than 1.5 mm but less than 4 mm (Clark's level IV: the tumor has spread to the lower dermis; T3N0M0).

Stage IIB

Localized melanoma that is greater than 4 mm (Clark's level V: the tumor has spread beneath the dermis; T4N0M0).

Stage III

The melanoma has spread to nearby lymph nodes or less than 5 in-transit metastases are found. An in-transit metastasis is metastasis that is located between the primary tumor and the closest lymph node region. It results from melanoma cells getting trapped in the lymphatic channels (any T, N1M0).

Stage IV

The tumor has metastasized to other parts of the body (any T, any N, M1 or M2).

TNM Levels

Thickness of the Primary Tumor (T)

:

T1:

The tumor is 0.75 mm or less in thickness and invades the upper dermis.

T2:

The tumor is more than 0.75 mm but not more than 1.5 mm in thickness and/or begins to invade the lower dermis

.
T3:

The tumor is more than 1.5 mm but not more than 4 mm in thickness and/or invades the lower dermis.

T3a:

The tumor is more than 1.5 mm but not more than 3 mm in thickness.

T3b:

The tumor is more than 3 mm but not more than 4 mm in thickness.

T4:

The tumor is more than 4 mm in thickness and/or invades the subcutaneous tissue (the tissue beneath the skin) and/or satellites within 2 cm of the primary tumor.

T4a:

The tumor is more than 4 mm in thickness and/or invades the subcutaneous tissue.

T4b:

The tumor satellites within 2 cm of the primary tumor.

Regional Lymph Node Involvement (N)

:

NX:

The regional lymph nodes cannot be assessed.

N0:

There is no regional lymph node metastasis.

N1:

Metastasis is 3 cm or less in greatest dimension in any regional lymph node(s).

N2:

Metastasis is more than 3 cm in greatest dimension in any regional lymph node(s) and/or there is in-transit metastasis. An in-transit metastasis is one that is located between the primary tumor and the closest lymph node region. It results from melanoma cells getting trapped in the lymphatic channels.

N2a:

Metastasis is more than 3 cm in greatest dimension in any regional lymph node.

N2b:

There is in-transit metastasis.

N2c:

Both N2a and N2b.

Distant Metastasis (M)

:

MX:

Distant metastasis cannot be assessed.

M0:

There is no distant metastasis.

M1:

Distant metastasis is present.

M1a:

Metastasis is in the skin or subcutaneous tissue or lymph node(s) beyond the regional lymph nodes.

M1b:

Metastasis occurs in other parts of the body.

Publication Review By: John J. Swierzewski, D.P.M.

Published: 31 Dec 1999

Last Modified: 24 Aug 2015