It is larger than the other birthmarks and it can spread to other parts of the body via the blood stream. These suspicious lesions need to be biopsied, that is have tissue removed for microscopic diagnosis, and in melanoma the biopsy should include complete removal. Melanomas tend to spread outwards across the skin or downwards into the skin. The latter types are more malignant. Malignancy can also be gauged by the total thickness of the melanoma.
Melanomas occur more in men than in women.
They tend to be on the trunk in men and on the legs in women. Those occurring on the upper back, the outside of the arms, the neck, or the skull tend to be more likely to spread than those occurring elsewhere. Frederick Edward Mohs, an American surgeon, introduced the technique of microscopically controlled serial excision of skin cancers, rather like the slicing of thin layers of meat in the delicatessen. Surgery is performed under local anesthesia with an initial debulking of the tumor followed by precise mapping of the slices and examination by frozen section for residual tumor. With melanoma, the excision may be wider and the regional nodes may be taken out, unless the disease is early.