What Does a Cancerous Toenail Look Like?

Reviewed on 8/24/2022
A doctor inspecting a person's toenail for cancer signs
Symptoms of a cancerous toenail may include brown-black discolorations of the nail bed, dark skin next to the nail, nail thickening, splitting nails, nail separating from the nail bed, bump or nodule under the nail, and destruction of the nail with pain and inflammation.

A cancerous toenail, also called toenail melanoma or subungual melanoma, is a subtype of malignant melanoma of the skin, but one which originates in structures within the nail. 

Subungual melanomas are rare and make up just 0.7% to 3.5% of all malignant melanomas worldwide. About 75% to 90% of reported cases of subungual melanoma occur in the big toe or thumb.

7 Symptoms of Cancer of the Toenail

A cancerous toenail may look like: 

  • Brown-black discolorations of the nail bed
    • Can look like a dark, narrow band in the nail
    • May look like a wide and irregular area of pigmentation
  • Dark skin next to the nail
  • Nail thickening
  • Splitting nails
  • Nail separating from the nail bed 
    • The white top edge of the nail will look longer as the nail lifts
  • Bump or nodule under the nail 
  • Destruction of the nail with pain and inflammation

What Causes a Cancerous Toenail?

The cause of cancerous toenails (subungual melanomas) is unknown. Unlike melanomas of the skin, it is not related to sun exposure. 

How Is a Cancerous Toenail Diagnosed?

A cancerous toenail (subungual melanoma) is diagnosed with a patient history and a physical examination of the toenail. 

Doctors often used “ABCDEF guidelines” to assess the risk of a pigmented nail lesion being a melanoma: 

  • Age: 50 to 70 years, and African, Japanese, Chinese, and Native American heritage
  • Brown-black band greater than 3mm with an irregular border
  • Change in size and growth rate
  • Digit: big toe, thumb, or index finger
  • Extension of discoloration into the skin surrounding the nail (Hutchinson sign)
  • Family histology of melanoma

If melanoma is suspected, a full-thickness biopsy of the nail bed is taken to confirm a diagnosis.

A lymph node biopsy may be performed to determine if the cancer has spread to lymph nodes.

What Is the Treatment for a Cancerous Toenail?

Treatment for a cancerous toenail (subungual melanoma) usually involves removal of the lesion (excision). The cancer must be removed with wide margins, which involves removal of the tumor and a wide margin of healthy surrounding tissue.

If the cancer has spread to lymph nodes, lymph nodes may be removed. 

Other treatments for cancerous toenail may include: 

  • Radiation 
    • Only used in specific circumstances
    • Reserved for use on the lymph nodes or brain metastases
  • Immunotherapy 


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Reviewed on 8/24/2022

Image source: Getty Images