SAN DIEGO (EGMN)-Of the many cases of longitudinal melanonychia - a longitudinal brown-black discoloration of the nail plate - only a fraction are subungual melanomas."With some of these you know they're going to require an extensive work-up or biopsy," Dr. Arash Izadpanah said at a melanoma update sponsored by the Scripps Clinic. "Others are not so concerning, but it's not always intuitive whether these are benign or malignant."In 2000, researchers led by Dr. Eyal K. Levit created a modified ABCDEF...