What are "margins" and how are they related to cancer treatment?

What are "margins" and how are they related to cancer treatment?

When a skin cancer is discovered, it needs to be removed, usually surgically. When a basal cell or a squamous cell carcinoma is removed surgically we have margins of normal skin that need to be taken along with the abnormal skin where the skin cancer is. That margin is anywhere from 2-5 millimetres usually depending on the size of the skin cancer. The bigger the skin cancer, the more irregular its growth pattern, and the wider the margin. In malignant melanoma, on the other hand, there are standards which are used which have to do with how invasive the melanoma is into the skin. When the melanoma is in situ or within the epidermis, generally a 0.5 centimetre or 1 centimetre margin is used. When the melanoma is less than 2 millimetres invasive into the skin, a 1 centimetre margin is usually used, and with anything above that a 2 centimetre margin is used. This is merely to ensure that the tumour is removed in total with some normal skin as a buffer for some abnormal cells which may be present in that area.