###Human: There is a thin black line on my finger nail. Is it skin cancer or melanoma? ###Assistant: Hi. I can understand your concern. I have gone through the attached picture (attachment removed to protect patient identity). Presence of linear pigmented lines on the nails can be due to multiple causes. In white people they are considered abnormal and require thorough assessment including biopsy. In dark skinned people it is a common variant. The most common cause of these lines is racial factors. Others being drugs, trauma, lichen planus, subungual nevi and malignant melanoma. You do not have to worry too much, but do keep a watch on the pigmentation. If you notice any variation within the pigmented line or pigmentation on the adjacent nail fold or finger pulp, then consult a dermatologist in person and get yourself evaluated. Regarding moles at other sites, it is sometimes possible that they can disappear. So you do not have to worry about that. For further queries, consult a dermatologist online -->