Metastatic patterns of malignant melanoma
In 2/3 of the patients, the first metastases are locoregional while 1/3 have distant metastases.
- Local recurrence – relapse in the scar or under the scar after the primary operation
- In-transit metastases – metastases which occur along the lymph pathways between the primary tumor > 2 cm from the scar and the regional lymph nodes
- Satellites – new tumor within a radius of 2 cm from the scar after removal of primary tumor. Satellites may be caused by remains of the primary tumor.
Satellites and in-transit metastases should give suspicion of distant metastasis.
Malignant melanoma can metastasize to almost all the regions of the body. One-third of patients have distant metastases without previous spreading to regional glands. Malignant melanoma can spread both hematogenously and through the lymphatic vessels.
The most common metastatic localizations are the skin, lymph nodes, lungs, liver, bone, and brain. The first metastases usually appear in the skin or lymph nodes, but metastases to the lungs, liver, and brain are the most common causes of death in patients with advanced malignant melanoma.
Melanoma in mucous membranes commonly metastasize to the liver, lungs, brain, and dermis. Local growth of tumor may be extensive with bone destruction and growth into the sinuses. Local recurrences are very common. 10-23% have lymph node metastases at the time of diagnosis and up to 25% will develop lymph node metastases in the disease course. Lymph node metastases are more common in oral malignant melanomas than for sinonasal. Five to 10% have distant metastases at the time of diagnosis.
Spreading of melanoma in the eye occurs almost always hematogenously since the eye lacks lymph drainage. In > 90% of patients, liver metastases are the first sign of disease dissemination (11).