There is a great deal of confusion about what the different prognostic factors in melanoma are. The initial pathology report usually includes most of the following (this may vary if the melanoma is invasive or just insitu – only in the superficial layer of the skin called the epidermis):
- Type of melanoma. There are about 5 or 6 different types but this has no prognostic value.
- Depth of lesion in Clark levels (1-5) – this has no prognostic value.
- The measured depth of the melanoma in mm (Breslow depth) – this is important in prognosis
- Ulceration: this is important.
- Mitotic rate: this is the rate at which the melanoma cells are dividing and does have a minor prognostic value.
- Vascular or perineural invasion: this is if the melanoma has spread around nerves or into blood vessels and can be a bad sign
- Regression – this is an indication of the body’s response to the melanoma – the jury is still out whether this is important or not.
- Margins from the edge of the melanoma to the edge of the excision. It is recommended that for in situ melanomas the distance be 0.5cm clinically and 1cm for invasive melanomas. Remember these are clinical margins and not the margins seen under the microscope. There is actually no evidence that any particular excision margin saves lives other than ensuring that the melanoma is all cut out.
Staging melanomas has an important role, especially in more advanced tumours. The current staging is from the AJCC, 6th Edition, 2002 and takes into account the thickness of the primary tumour (Breslow) with or without ulceration, whether the tumour has spread to nodes, and whether it has spread to other organs.
- Stage 1 is insitu melanoma
- Stage 2 is invasive melanoma with no nodes or distant metastasis
- Stage 3 is melanoma with nodes but no other metastasis
- Stage 4 is with distant metastasis.