Black nails are not necessarily cancer, of course, black nails are common malignant melanoma, in addition to black nails around the nail skin can also appear black, can appear erosion, ulcers, bleeding, pain and other manifestations of the above symptoms should be promptly consult a doctor to avoid delays in the condition. In addition to cancer, subnail hemorrhage is also a common cause of black nails, good in the toes, especially the bunion often due to extrusion, bleeding symptoms, manifested as black nails, you can go to the hospital to do a dermatoscopy examination to confirm the diagnosis. In addition to under-nail bleeding, nail fungus disease she is caused by fungal infection, can also appear nail color changes, can be yellow or black.