Melanoma: determining the stage of the cancer

Superficial spreading melanoma of the lower leg.    Photo courtesy Dr. S. G. Green

Once the treating physician has received a pathology report with a diagnosis of melanoma he or she takes that information and stages the disease.

Stage I:

Ia: The melanoma is less than 1.00 mm in Breslow's thickness without ulceration (loss of the surface cells to form a sore) and is in Clark's level II or III.

Ib: The melanoma is less than 1.00 mm in Breslow's thickness with ulceration, and/or Clark's level III or IV, or is 1.01-2.00 mm in thickness without ulceration and may have spread to the closest lymph nodes.

Stage II:

IIa:  The melanoma is 1.01-2.00 mm in Breslow's thickness and has ulceration, or is 2.01-4.00 mm in thickness without ulceration.

IIb:  The melanoma is 2.01-4.00 mm in Breslow's thickness and has ulceration, or is greater than 4.00 in Breslow's thickness without ulceration.

IIc:  The melanoma is greater than 4.00 mm in Breslow's thickness, and is also ulcerated.

Sentinal node biopsy:  The lymphatic vessels and lymph nodes fun roughly parallel to the blood vessels and carry fluid and immune cells around the body, generally toward the trunk.  A tumor which spreads via the lymphatics will be caught by the next lymph node and held there ( the "local" nodes).  Eventually the cells will move further in the lymphatics, eventually reaching the major clusters of nodes, which would be in the armpit for the arms and in the groin for the legs ( "regional" nodes).  If there is any indication that a tumor which seems in the early stages could have spread to the lymph nodes a sentinal node biopsy may be performed.  This is a special test that is performed on the melanoma before the final surgical removal to determine whether there are melanoma cells which have spread to the closest lymph node draining the tumor area (the "sentinal node").  It is done by injecting a small amount of radioactive dye into the skin next to the tumor which would generally lead to the lymph node.  As an example, a melanoma of the arm will spread upwards toward the shoulder and a leg will spread up toward the groin.  Some areas of the body, such as the back, are less predictable and may have lymphatic drainage in any direction and will be injected and scanned in all directions from the tumor.  The radioactive signal is concentrated in the nearest lymph node and is found with a special type of radiation meter.  The node is then marked and surgically removed through a small incision and sent to a pathologist for examination.  If the node does not have melanoma in it no further nodes are removed.  If there is melanoma then further nodes will be explored and removed.

Stage III:  This stage indicates that the melanoma has spread to the local or regional lymph nodes or cells from the tumor have spread through the lymphatics and formed new, metastatic tumors (also called satellite tumors ) in the skin more than 2 cm ( 0.8 inches) from the original cancer, but not further than the regional lymphnodes. This includes tumors which can only be seen under the microscope.

Stage IV: The melanoma has spread to lymph nodes far from the original cancer, or has spread to involve other organs. The organs usually involved (in order from most to least likely): lung, liver, brain, bone, and gastrointestinal tract.

 

For more info: see the Skin Cancer Foundation website.