Mortality is low compared to other cancers, but has increased in the last ten years. After removal of the primary tumor, over 80% of patients operated for malignant melanoma are cured. However, the prognosis depends on whether the disease is localized, regional, or metastatic at the time of diagnosis.
With localized disease, the thickness of the melanoma is the most important prognostic factor. For localized malignant melanoma, the prognosis has improved considerably in the last few years. Five-year survival has increased from approximately 65-90% (1). The improvement in prognosis is attributed to earlier diagnosis. For regional and metastatic diseases, the survival rate has improved minimally (1).
In-transit metastases and satellites should give suspicion of distant metastases and are associated with poor prognosis. For in-transit metastases and satellites, the expected five year survival is 50% without lymph node metastases, and 30% with lymph node metastases.
The prognosis with lymph node metastases is dependent on the number of glands containing tumor tissue. In patients with spreading to only one gland, the ten year survival is almost 50% after radical lymphadectomy. If there are metastases in 2-4 glands the prognosis is more serious, and the 10 year survival is 20-30% after surgery (9).
The mortality rate is somewhat higher for men than for women.
Elderly patients have a poorer prognosis than younger patients.
The localization of the melanoma also has prognostic significance. For example, prognosis is better for melanoma localized to the face, neck and lower extremities. Melanoma localized on the foot, hand, and sublingually has the poorest prognosis.
For melanoma in the eye, the mortality rate is 30-50% depending on the size and localization of the tumor (11).
Five-year relative survival for patients with melanoma (skin), in percent, during the diagnosis period 1974–2013.
Source: Cancer Registry of Norway
Prognostic factors for skin melanoma
- Vertical thickness of primary tumor. The Breslow thickness is the most important prognostic parameter as long as metastases are not present at the time of diagnosis.
- Ulceration. The prognosis is worse in cases of ulceration (9,10).
- Mitotic rate. Tumor cell proliferation measured by mitotic rate is an independent prognostic factor for the thinnest melanomas. The presence of > 1 mitosis / mm ² predicts a poorer prognosis.
- Regional and metastatic disease. Metastases to regional lymph nodes will lead to a drastic fall in five year survival. The number of metastatic glands greatly influences the prognosis. For distant metastases, the chance of survival is < 10%. The prognosis is best if the metastatic spreading is to the skin, subcutanous tissue, lymph nodes, and lungs. The prognosis is the poorest in cases of spreading to the brain and liver.
Prognostic factors for malignant melanoma in mucous membranes
- Tumor thickness. This is the most important prognostic indicator. Lesions with thickness < 0.75 mm metastases are rare. Lesions with thickness > 5 mm have a poor prognosis.
- Vessel infiltration. This is a significant prognostic factor and predicts local relapse, regional metastases, and distant metastases, as well as disease-free survival.