I had a podiatry appointment a few days ago and she asked about a black line down my big toe nail. It has been there for at least a year but not caused any problems so I had just ignored it. The podiatrist emailed my GP who asked for a photo (he is still doing virtual appointments) and he has referred me urgently to a dermatologist. I have since started to worry about a  similar line down a finger nail that has been there for a while. Is it likely that a melanoma would present in two different nails at the same time?