Subungual melanoma is a rare type of skin cancer that occurs under the nails. Symptoms include streaks on the nails, color changes in or around the nail, a bruise under the nail that does not heal, and the nails separating from the nail bed.

Melanoma can affect any area of the skin. It starts when melanocytes, a type of skin cell, become cancerous. Melanoma is a particularly serious form of cancer because it can rapidly spread to other organs without early detection and treatment.

Subungual is a type of melanoma that starts under the nails. “Subungual” is a Latin word meaning “beneath the nail or claw.” The early signs of subungual melanoma are not always noticeable when they occur under the nails. This makes subungual melanoma particularly difficult to detect and treat early.

In this article, we discuss subungual melanoma, which is a type of cancer that can affect the nails.

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Melanoma is a cancer of the skin that begins in the melanocytes, which are the cells responsible for skin pigment. Collections of melanocytes can form moles. Some moles are cancerous, but many are not.

Melanoma can be difficult to treat if not identified in its earliest stages, as it can spread throughout the body.

Melanoma is usually the result of exposure to excess sun and ultraviolet radiation, so most people identify melanoma on parts of the body where the sun hits, such as the face.

A person may be less likely to suspect melanoma in other areas of the skin. This includes melanoma under the fingernails, which is known as subungual melanoma.

This type of melanoma may be challenging to identify because it often resembles normal bruising of the nails.

There are different types of nail-related melanoma. Subungual melanoma originates in the nail matrix, which is where keratin forms. Other nail-related cancers include ungual melanoma, which develops underneath the nail plate, and periungual melanoma, which originates in the skin next to the nail plate.

Around 0.7% to 3.5% of melanoma cases are subungual worldwide.

Subungual melanoma often starts as a brown or black streak under a toenail or fingernail. A person may mistake it for a bruise.

The main symptoms of subungual melanoma include:

  • brown or black streaks in the nail without any known injury
  • streaks on the nails that increase in size
  • a bruise on the nail that will not heal or move up as the fingernail grows
  • fingernails or toenails that separate from the nail bed
  • darkening skin next to the nail
  • a nail that bleeds or develops a nodule
  • thinning, cracking, or distortion of the nail plate

One of the key indications of subungual melanoma is “Hutchinson’s sign.” This is when a person has nail pigment that extends onto the skin surrounding the nail.

Subungual melanoma occasionally occurs without the distinctive pigmented streaks. In these instances, a person may experience other symptoms associated with subungual infections, including changes to the nail itself, bleeding, and pain at the nail bed.

Having certain risk factors does not necessarily mean someone will get subungual melanoma. However, it does mean they have a greater chance of developing the condition and should be especially vigilant for early symptoms.

The most significant risk factor for melanoma is prolonged exposure to the sun and ultraviolet light. However, subungual melanoma appears to be unrelated to sun exposure.

Other risk factors for melanoma include:

  • having many moles or abnormal moles
  • having fair skin and light hair
  • having freckles
  • having a family history of melanoma or other skin cancers
  • having a condition that causes a weakened immune system, such as HIV
  • being older
  • being male

It is also important to note that subungual melanomas are the most common type of melanoma among African Americans. It is the most common variant of malignant melanoma among African Americans, Asians, and Hispanics. It accounts for 75% of melanomas in African populations, 25% in Chinese populations, and 10% in Japanese populations.

A doctor will conduct a physical assessment of the fingernail and ask questions about symptoms.

They may ask when the nail streaking began, how the nail has changed over time, and whether a person has any relevant medical history.

Some conditions that may look similar to subungual melanoma include:

If a doctor suspects the condition could be subungual melanoma, they will biopsy the nail matrix and nail bed.

A pathologist specializing in identifying cancerous cells will examine the nail cells to determine if they are cancerous and consistent with the appearance of melanoma.

If a doctor confirms the diagnosis is melanoma, they may order more tests to determine if the cancer has spread.

A doctor will then stage the melanoma based on how many cancerous cells are present and how the melanoma has spread.

The subungual melanoma may be melanoma “in situ,” meaning it is only in the top layer of skin.

The most severe form of subungual melanoma is stage 4, where the cancer cells have spread to other organs.

Once a doctor determines the severity of subungual melanoma, they will usually start treatment by surgically removing the affected area. This may include removing the entire nail or a portion of the digit.

If the cancer has spread to the lymph nodes or throughout the body, it may be too extensive to treat by just removing the affected area.

Following the surgical removal of the affected area, a doctor may recommend further therapies to help prevent the subsequent spread of the cancer. These treatments may include radiation and chemotherapy.

When an injury bursts blood vessels under the nail, it causes a red-purple mark to appear. This is known as a subungual hematoma. Common sources of this injury include trapping a fingernail in a closing door and wearing tight shoes.

Subungual hematomas can be mild to severely painful. They might also lead to infections, which cause symptoms that include fever and inflammation.

Subungual hematomas are not cancerous, but they cause symptoms that can look similar to those of subungual melanoma. People who develop persistent dark marks under a nail should check in with a doctor to be safe. This is particularly important if the symptoms arise without a known injury.

The symptoms of subungual melanoma can be easy to miss, as they are underneath the nails. For this reason, people typically receive a diagnosis at a later stage than with other forms of melanoma.

The outlook for subungual melanoma will vary depending on its stage at the time of diagnosis and treatment.

The American Cancer Society states that 99% of people with melanoma that has not spread will survive for at least 5 years following a diagnosis. This 5-year survival rate falls to 66% for melanomas that spread regionally and 27% for melanomas that spread to distant organs.

Subungual melanoma is a type of skin cancer that develops beneath the nails. Melanomas are particularly serious because they can quickly spread throughout the body. Subungual melanomas can be harder to detect than other melanomas due to their symptoms occurring under the nails.

Subungual melanoma is the most common type of melanoma among African Americans.

Melanoma is highly treatable when doctors can identify the condition before it spreads. However, people with subungual melanoma typically receive a late diagnosis, when the cancer may have already spread around the body.