Swollen lymph node in the armpit of a 77 year old man with metastatic melanoma. Melanomas are invasive cancers, and may spread to other parts of the body (metastasis). If this occurs, the prognosis is poor. Here, the primary cancer is on the neck. Melanomas are the most dangerous form of skin cancer. The lymph nodes and other glands are commonly affected by cancer as it spreads from its primary site. Around the armpit are seborrheic warts, which are benign (non-cancerous).