What Is Medical Definition of Malignant Melanoma in Situ?

A malignant melanoma is a cancer that originates in skin cells called melanocytes, states MedicineNet. A malignant melanoma "in situ" refers to a melanoma that is limited to the upper level of the skin's epidermis, otherwise referred to as Stage 0 cancer, states AIM at Melanoma Foundation.

In cases of melanoma in situ, the cancer cells have not spread from the upper layers of skin and have not shown indication of spreading, states AIM at Melanoma Foundation. After removal there is a very low risk the cancer will metastasize or recur, and the overall survival rate with treatment is 99 to 100 percent after five to ten years.

Treatment for melanoma begins with removal of the tumor, according to the Skin Cancer Foundation. The general method of removal is by surgical excision or resection. As of 2015, for Stage 0 melanoma the surgeon will remove the tumor itself plus a margin of 0.5 to 1 cm of the surrounding skin. Depth-wise, the skin layers going down to the layer of fat will be removed. The excision is normally done in a doctor's office or in an outpatient procedure with local anesthetic. The patient will have sutures for one to two weeks and will generally be advised to avoid heavy exercise during that time.