Nodular melanoma is a type of skin cancer. It’s a firm, raised, discolored growth on your skin that may look like a blood blister. Overexposure to ultraviolet light is the primary cause of nodular melanoma. It exists in four stages.

A blood blister is a raised pocket of skin that looks like a friction blister. But blood blisters are filled with blood instead of clear fluid. They may appear red, purple or black. Blood blisters form when you injury yourself, such as pinching your finger. Blood blisters typically heal on their own and don’t require treatment.

Blood blisters appear as raised, fluid-filled sacks on the skin and look very similar to friction blisters. Unlike friction blisters that contain a clear liquid, blood blisters contain a red fluid. The liquid begins as a light red color that becomes darker over time. Most blood blisters will cause minor irritation at the site of the blister.