Dr Ian Webster explains the process of a malignant melanoma diagnosis, and when exactly one is referred to an oncologist.
Approximately 1 in 50 white South Africans will develop a malignant melanoma in their lifetime. Therefore, it’s a reasonably common skin cancer which can also affect young people.
Unfortunately, the incidence of malignant melanoma in people with a pale skin is still rising worldwide.
Subtypes of malignant melanoma
- Superficial spreading melanoma is the easiest to recognise. It is usually greater than 7mm in size, irregular edge and irregular colour, and initially grows sideways and then downwards.
- Nodular melanoma usually presents as a round dark mole. However, it is more aggressive as it grows downward into the dermis from the start.
- Lentigo maligna melanoma tends to occur in older patients. This type of melanoma arises from a darker freckle, usually on a sun-exposed area.
- Acral lentiginous melanoma is the most difficult to diagnose as it often presents with a freckle on the palms, or the soles of the feet. This type of melanoma is more common in people with a darker skin.
Your chances of survival are excellent if the malignant melanoma is caught at an early stage i.e. a thin melanoma. However, the deeper the melanoma penetrates in to the skin, the worse the prognosis.
When pathologists look at a biopsy of a malignant melanoma, they measure what we call Breslow’s thickness. This is the depth in millimetres from the top layer of the skin to the bottom of the tumour in the dermis.
How a melanoma is diagnosed
If you’re concerned about any moles on your body, you should make an appointment with a dermatologist.
If your dermatologist picks up, on examination, a suspicious looking mole or nevus, he/she will often do the initial excision biopsy.
The skin specimen is then sent to a dermatopathologist, who will determine if the mole is benign or malignant.
If the mole is malignant, the Breslow’s thickness will be measured. If it is more than 1mm then your dermatologist will refer you to a plastic surgeon. He/she will do a wider excision, as well as a sentinel lymph node biopsy which will determine if it has spread to the regional lymph nodes. The surgeon injects a radioactive dye near the melanoma and follows it to the nearest lymph node. Then the surgeon will surgically excise the lymph node and send it to a pathologist.
Therefore, a dermatologist or general practitioner will make the initial diagnosis of a melanoma. They will then refer you to a plastic or general surgeon for a wider excision, if necessary.
Stage IIB melanoma
If the melanoma is a Stage IIB i.e. Breslow’s thickness greater than 2mm but with no positive regional lymph nodes and no distant metastases, the dermatologist or surgeon will then refer you to an oncologist.
An oncologist will often recommend further blood tests and various body scans. They would discuss various options with you and may offer adjuvant immunotherapy with interferon-alpha as a treatment option.
Stage IV melanoma
If your malignant melanoma is a Stage IV with distant metastases, then your oncologist would offer you systemic treatment. This may include targeted therapy, immunotherapy and chemotherapy.
BRAF V600 mutation
Approximately 50% of patients with malignant melanoma carry an activating BRAF V600 mutation, for which several highly-selective inhibitor drugs have been developed.
Higher risk of developing more
If you have developed one melanoma, there is unfortunately a higher risk of developing another malignant melanoma. It is therefore very important, even if you are under the care of an oncologist, to return to see a dermatologist, for a total body skin examination, with or without mole mapping.
MEET OUR EXPERT – DR IAN WEBSTER
Dr Ian Webster MB ChB (UCT) FF Derm (SA) is a dermatologist. He has been in private practice for the past 24 years in Cape Town. He has a special interest in skin cancer and skin laser surgery.
European Dermatology Forum: Guideline on the Diagnosis and Treatment of Melanoma 09/2015