Stages of melanoma

There are two aspects to the doctor’s staging of the melanoma: first he wants to know that the disease is localised (i.e. has not spread) and so he examines the patient thoroughly to ensure that he cannot find any evidence of spread. In particular, he examines the patient’s lymph nodes in the area to which the melanoma skin site will drain (e.g. the skin of the leg will drain to the groin lymph nodes and the doctor will pay particular attention to the groin nodes on that side to see if they are abnormally enlarged).

 

Additionally, he will perform a chest x-ray and liver scan as well as a whole body PET (positron emission tomography) scan to complete the staging. He will also perform blood tests and a urinary melanogen screen after resection of the primary may be useful as no patient who has localised disease will continue to excrete this pigment after the lesion has been excised unless there is undetected (on physical exam and on scanning) spread.

 

The serum levels of a protein called S-100 can also be prognostic, but neither of these marker tests are properly validated at this time.

 

The other aspect of staging is that of the extent of the primary melanoma, a predictive (prognostic) value in disease that is localised to the skin (i.e. staging for spread has proved negative). It is now realised that the depth of skin invasion is of major predictive/prognostic import.

 

Thus the staging is based on the depth/thickness of invasion for stages 1-2 disease; the overall staging is thus:
Stage 1A. Localised: Less than 0.75mm depth.
Stage 1B.Localised: 0.76-1.5 mm depth.
Stage 2A. Localised: 1.5 - 4mm depth.
Stage 2B. Localised: More than 4mm depth.
Stage 3. Nodal metastases in the regional draining nodes (vide supra).
Stage 4. Metastatic disease to other organs.

 

The staging is prognostically very predictive; thus, patients with stage 1 disease have a 90% ten year survival, stage 2 has a 60% and stage 3 has a 30% ten year survival. Only five per cent of patients with stage 4 disease survive five years.