What is the most dangerous form of skin cancer, known for appearing as dark brown or black spots?

Malignant melanoma is the most dangerous form of skin cancer primarily due to its tendency to spread rapidly to other parts of the body if not detected and treated early. It often presents as dark brown or black spots on the skin that can vary in size and shape. These spots may also have irregular borders and be uneven in color. Early detection is crucial for effective treatment, as timely intervention can significantly increase survival rates.

In contrast, squamous cell carcinoma and basal cell carcinoma, while they can also be serious, are typically less aggressive than melanoma and have a lower likelihood of metastasizing. Basal cell carcinoma generally appears as a small, pearly bump or a sore that doesn't heal, while squamous cell carcinoma can appear as red, scaly patches or warts. Excoriation refers to the act of scratching or damaging the skin, rather than a type of skin cancer.