How do you tell the difference between a subungual hematoma and a malignant melanoma?

This is a very important distinction to make because a melanoma can have a high mortality rate if diagnosed late. One should have a high suspicion for a melanoma, if pigment develops in a single nail of a person aged 50 to 80 years old. Also, any band in the nail that is wider at the base or darkening is worrisome. Hutchinson’s sign, the leaching of pigment into the surrounding nail fold, is considered pathognomonic. Hematoma pigment remains confined to the nail bed and gradually grows out with the nail. Melanonychia (longitudinal pigmented lines on nails) is also very common in individuals with darker skin and is a more likely diagnosis if multiple nails are affected, the lines are well demarcated laterally, they are not changing, and Hutchinson’s sign is negative.