New Melanoma Staging System – By means of an unprecedented cooperative effort among cancer centers around the world, the classification system recommended by the American Joint Commission on Cancer (AJCC) was updated on January 1, 2018. New findings about melanoma were incorporated to provide the most accurate diagnosis and prognosis (a forecast of how the disease is likely to progress).
The thickness of the tumor, known as Breslow thickness or Breslow-depth, and the appearance of microscopic ulceration (meaning the epidermis on top of a major portion of the melanoma is not intact) continue to be the most important factors in staging primary melanoma tumors, while mitotic rate, the speed of cell division (how fast-growing the cancer cells are), has been dropped as a staging criterion for stage I tumors.
|Two examples of thin melanomas|
To be exact, Breslow thickness measures in millimeters (1 mm equals 0.04 inch) the distance between the upper layer of the epidermis and the deepest point of tumor penetration. The thinner the melanoma, the better the chance of a cure. Therefore, Breslow thickness is considered one of the most significant factors in predicting disease progression.
• In situ (noninvasive) melanoma (stage 0) remains confined to the epidermis.
• As of January 1, 2018, invasive tumors continue to be considered early and thin (stage I) if nonulcerated and less than 1 millimeter (mm) in Breslow depth. However, tumors that are greater than .8 mm in Breslow depth (or under .8 mm but ulcerated) are now considered concerning enough to have moved from category T1a to T1b, and may be considered for sentinel lymph node biopsy to verify whether melanoma cells have spread to the local lymph nodes.
• Intermediate, high-risk (stage II) tumors are 1.0 to 4.0 mm and/or are ulcerated. They are at high risk of spreading (metastasizing) to nearby lymph nodes or beyond, and patients are typically advised to undergo sentinel lymph node biopsy.
• Thick melanomas (still clinically stage II, but at very high risk of metastasizing) are greater than 4.0 mm, and patients are typically advised to undergo sentinel lymph node biopsy.
The presence of microscopic ulceration upgrades a tumor’s seriousness and can move it into a later stage. Therefore, the physician may consider using a more aggressive treatment than would otherwise be selected for a tumor that size.
Stage III. By the time a melanoma advances to Stage III or beyond, an important change has occurred. Breslow thickness is by then irrelevant and is no longer included in staging, but the presence of microscopic ulceration continues to be used, as it has an important effect on the progression of the disease. At this point, the tumor has either spread to the nearby lymph nodes or to the skin between the primary tumor and those lymph nodes. (All tissues are bathed in lymph — a colorless, watery fluid consisting mainly of white blood cells — which drains into lymphatic vessels and lymph nodes throughout the body, potentially carrying cancer cells to distant organs.)
A tumor is assigned to Stage III if it has metastasized beyond the original tumor site. This can usually be determined by examining a biopsy of one or more lymph nodes nearest to the tumor, known as the sentinel nodes. Such a biopsy is frequently done when a tumor is .8mm or more in thickness, or when a thinner melanoma shows evidence of ulceration. As the sentinel node biopsy is not considered necessary in all cases, you may wish to discuss the matter with your physician.
In-transit or satellite metastases are also included in Stage III. These metastases spread to skin or underlying (subcutaneous) tissue more than 2 centimeters (1 cm equals 0.4 inch) from the primary tumor, but not to the regional lymph nodes.
In addition, the new staging system includes metastases so tiny they can be seen only through the microscope; formerly called “micrometastases,” They are now referred to as “clinically occult disease.” Just how advanced the tumor is into Stage III (the “N” category, for “nodes”) depends on factors such as whether the metastases are in-transit or have reached the nodes, the number of metastatic nodes involved, the number of cancer cells found in them and whether or not they are clinically occult disease or can be seen with the naked eye.
Stage IV. The melanoma has metastasized to lymph nodes distant from the primary tumor or to internal organs, most often the lung, followed in descending order of frequency by the liver, brain, bone and gastrointestinal tract. The two main factors in determining how advanced the melanoma is into Stage IV (the “M” category, for “metastases”) are the site of the distant metastases (nonvisceral, lung or any other visceral metastatic sites) and whether or not the serum lactate dehydrogenase (LDH) level is elevated. LDH, an enzyme found in your blood and almost every other cell of your body, turns sugar into energy, and the more you have in your blood or other body fluid, the more damage has been done to your body’s tissues.