Finding black or brown spots underneath your toenails can be very concerning for people, especially after doing a Google search. The good news is that these discolorations are usually from some other cause and are not skin cancer (melanoma). You can relax now, but it is still important to have your toenail examined by a medical professional such as a podiatrist or dermatologist for further evaluation and treatment.

Subungual Melanoma are a rare type of skin cancer that can develop beneath the surface of the nail. Called subungual (under the nail) melanoma, it generally appears as a brown or black longitudinal streak. These streaks are usually 2-3 mm but can be wider. An important feature of subungual melanoma is that the streaks do not grow out with the nail.  People often dismiss the pigmentation as a bruise thinking they just bumped into something or injured the toenail somehow without realizing it. This can cause a delay in diagnosing it at the earliest stage where it would be more easily treated. Because diagnosis of melanomas is often delayed it can progress to advanced stages more frequently than other types of skin cancer.

While the exact cause of development of subungual melanomas is unknown potential causes may include:

  • Trauma to the nail bed itself
  • Bacterial or fungal infections of the nail bed
  • Weakened immune systems due to immunosuppressant drugs or disease
  • A familial history of melanoma or other related cancerous tumors

If a doctor suspects the discoloration on your toenail could be a subungual melanoma, they will take a biopsy of the nail matrix (root), as well as the nail bed. The biopsy will then be sent to a pathologist specializing in identifying cancerous cells who will examine the nail cells to determine if they are cancerous.

If you notice a concerning discoloration on your toenail come see one of our Doctors and Foot and Ankle Associates of North Texas.

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