Melanoma Skin Cancer
This type of skin cancer accounts for around 5% of skin cancer cases. Melanomas are tumors comprising of malignant melanocytes, the skin cells that form the pigment melanin. Nevi (“moles”) are benign melanocytes which have multiplied and grouped together. Rarely melanoma can also be pink or not pigmented and then it is called amelanotic melanoma. Any pigmented lesion (darker than normal skin) exhibiting the following features should be treated as suspicious and should be examined clinically and preferably dermatoscopically by a physician:
- A – asymmetry of structure and color
- B - Border irregularity
- C – Color variance in the lesion
- D – Diameter 6 mm. or more
- E – Evolving lesion – recent noticeable change
Management of Melanoma
Melanoma can be classified by its Breslow thickness and this is currently the main determinant of the level of intervention needed following initial diagnosis. The Breslow thickness is the distance measured from the top of the skin lesion (stratum granulosum level of epidermis) to the deepest tumor cells. Other factors include the mitotic rate (how fast cancer cells divide and grow) and evidence of ulceration.
Breslow Depth and current recommended clinical margins:
- In situ carcinoma - 0.5 cm.
- < 1mm. – 1cm.
- 1-2mm. – 1-2 cm.
- 2-4mm. – 2 cm.
- > 4mm. – 2 cm.
These recommended margins usually mean that after the diagnosis of melanoma another procedure would be needed to achieve the above margins. This is called a Wide Local Excision (WLE).
Sometimes local lymph nodes will be biopsied (this is called a Sentinel Lymphnode Biopsy) to determine spread to the lymph nodes. Other investigations for instance CT or PET scans can also be indicated to look for local or distant metastases. Following the re-excision and if performed, the sentinel lymphnode biopsy the stage of the melanoma can be determined and this would determine if further treatment is indicated and what the prognosis would be. Chemotherapy, and more recently immunotherapy are possible treatments for advanced stage melanoma.
For more information, see Management of Skin Cancer.
If a patient was diagnosed with melanoma a Skin Screening Exam is indicated 3 monthly for the first 2 years and then every 6-12 months for the lifetime of the patient. The main aim is to detect any new melanomas and to check for local or distant metastasis from the original tumour site. Mole Mapping is indicated in patients with a new diagnosis or a history of melanoma.