The differences between toenail bruise and melanoma are different causes, different symptoms, different prognosis and treatments. 1. Pathogenesis: toenail bruise is caused by the collision or extrusion of toenail, which leads to the rupture of capillaries inside the toenail, and the blood coagulates and forms inside the toenail. Melanoma is a malignant tumor produced by the malignant transformation of epithelial cells. 2. Symptoms: the symptom of toenail bruise is the appearance of greenish-purple or dark-purple spot or patchy bruise, which may be accompanied by pain when it first occurs. The symptoms of melanoma are that the nail plate ruptures and starts to turn black gradually, and then a black-brown lump appears, after which there will be localized ulceration, nail rupture, and blood and water outflow, and so on. 3. Prognosis and treatment: toenail bruise generally needs no treatment, with the passage of time, the bruise will be slowly absorbed, and the toenail can be restored to normal. On the other hand, melanoma will not recover on its own and needs to be treated by surgery or radiotherapy. If the patient’s toenails are abnormal, he should consult a doctor in time, do a systematic examination, and strictly follow the doctor’s instructions for treatment.