Stage 4 melanoma is defined when the melanoma has spread beyond the original site and regional lymph nodes to more distant areas of the body. The blood level of LDH (serum lactate dehydrogenase) in the patient may or may not be elevated. The significance of this is that it provides biochemical evidence of metastatic spread. The most common sites of metastasis are to vital organs (lungs, abdominal organs, brain, and bone), soft tissues (skin, subcutaneous tissues) and distant lymph nodes (lymph nodes beyond the primary tumour region).
