The stage of a melanoma determines the depth of the lesion in the skin and whether it has metastasized. This is determined though a biopsy and imaging tests. The results of these tests and the subsequent staging of the disease is important in determining the type of treatment required (if any), and the prognosis.
Staging is determined by the following;
· Clark scale : the depth of the melanoma within the layers of the skin
· Level 1-melanoma in situ – the melanoma cells are only in the outer layer of the skin (the epidermis)
· Level 2 -melanoma cells in the layer directly under the epidermis (the papillary dermis)
· Level 3 -melanoma cells are throughout the papillary dermis and touching on the next layer down (the reticular dermis)
· Level 4-melanoma has spread into the reticular or deep dermis
· Level 5-melanoma has grown into the layer of fat under the skin (subcutaneous fat)
· Breslow scale: measures the thickness of the melanoma in the skin
· TNM staging of melanoma describes the thickness of the melanoma and whether there is any spread to lymph nodes or other parts of the body. TNM stands for Tumour, Node, and Metastases. This staging system describes the size of a primary tumour (T), the extent of the disease in the lymph nodes (N) and whether a metastiasis has occured (M). The T part of the TNM describes the thickness of the melanoma (primary tumour) according to the Breslow scale.
There are 5 stages of tumour size in melanoma according to the thickness of the lesion;
· Tis – melanoma in-situ; involves skin surface only
· T1 – less than 1 millimetre
· T2 – between 1 mm and 2 mm
· T3 – between 2 mm and 4 mm
· T4 – more than 4 mm
Each stage is further classified a or b depending on whether the tumor is ulcerated.
There are 4 stages depending on lymph involvement;
· N0 – no melanoma cells detercted in the nearby lymph nodes
· N1 – melanoma cells found in one lymph node
· N2 – melanoma cells in 2 or 3 lymph nodes
· N3 – melanoma cells found in 4 or more lymph nodes
Each stage is further classified as a, b or c, depending on whether it is a macrometastasis, micrometastasis, or satellite/ in transit metastases.
There are 4 stages depending on the extent of the disease;
MO- no metastases detected
M1a- melanoma has progressed to areas outside where the primary lesion occurred
M1b- metastases found in the lung
M1c- metastases detected in other organs
· Number stages of melanoma group together the depth of the melanoma and the TNM staging in a simpler way
Stage 0 (in situ melanoma)
Melanoma cells are only in the top surface layer of skin cells (the epidermis) and have not started to spread into deeper layers.
less than 1mm thick, and not ulcerated.
less than 1mm and ulcerated or it is between 1 and 2mm and is not ulcerated.
between 1 and 2 mm thick and is ulcerated., or it is between 2 and 4mm and is not ulcerated.
between 2 and 4mm thick and is ulcerated, or it is thicker than 4mm and is not ulcerated.
The melanoma is thicker than 4mm and is ulcerated.
The melanoma has spread into up to 3 lymph nodes near the primary tumour.
· The melanoma is ulcerated and has spread to between 1 and 3 lymph nodes.
· The melanoma may or may not be ulcerated and has spread to 4 or more nearby lymph nodes
Melanomas have spread further than the primary site and the nearby lymph nodes.