It is very common for patients to present with a discoloration of a toenail and are concerned about a melonoma. The above picture is an example of a patient who presented to me with discoloration to the right great toenail as a resulted of concern by the family doctor.
Most of the time this discoloration is secondary to bleeding under the nail plate from micro trauma from shoe gear or a thick toenail. The only way to rule this out is to remove the toenail and look to see if there are any pigmentation changes to the nail bed. In this particular case you can see there are none.
The photos below are all pictures of benign lesions to the nail plate.
These two lesions that follow look almost exactly alike. One is a malignant melanoma and one is not.