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, which makes subungual melanoma particularly difficult to detect and treat early.

This article explains subungual melanoma, including symptoms, treatment options, and the general outlook.

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Melanoma is a cancer of the skin that begins in the melanocytes, 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 (UV) 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 or toenails, known as subungual melanoma.

This type of melanoma may be challenging to identify because the discoloration can resemble bruising of the nails.

There are different types of nail-related melanoma. Subungual melanoma originates in the nail matrix, 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 0.7–3.5% of malignant melanoma cases are subungual worldwide.

Subungual melanoma may start 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 UV light. However, subungual melanoma may 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
  • a family history of melanoma or other skin cancers
  • 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 the following populations:

  • African American people
  • Asian people
  • Hispanic people

It accounts for 75% of melanomas in African populations, 25% in Chinese populations, and 10% in Japanese populations.

To diagnose subungual melanoma, a doctor will conduct a physical assessment of the fingernail. They may ask when symptoms, 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 a melanoma diagnosis, they may order more tests to determine if the cancer has spread. A doctor will 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.

Subungual melanoma vs. hematoma

When an injury bursts blood vessels under the nail, a red-purple mark appears. This is a subungual hematoma. Potential sources of this injury include trapping a fingernail in a closing door or wearing tight shoes.

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

Subungual hematomas are not cancerous, but they cause symptoms similar to those of subungual melanoma.

People with 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.

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

If the cancer affects the lymph nodes or other body parts, it may be too extensive to treat by 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, including radiation and chemotherapy.

Subungual melanoma symptoms can be easy to miss as they occur 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 varies depending on its stage at the time of diagnosis and a person’s response to treatment.

The American Cancer Society states that more than 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 74% for melanomas that spread regionally and 35% for melanomas that spread to distant organs.

Below are some common questions about subungual melanoma.

What does nail melanoma look like in the beginning?

Early-stage subungual melanoma can cause brown or black streaks or discoloration underneath the nail that looks like a bruise. People may experience other changes to the nail, such as streaks or separation from the nail bed.

What can be mistaken for subungual melanoma?

Other conditions, such as a fungal nail infection or subungual hematoma, can resemble subungual melanoma. However, people should seek a diagnosis in case of subungual melanoma since early diagnosis and treatment may improve outcomes.

How fast does nail melanoma progress?

Progression rate may vary from person to person. Subungual melanoma may appear to progress quickly because many people do not discover it until the later stages.

Is subungual melanoma curable?

The outlook for subungual melanoma may depend on the stage and a person’s response to treatment. If diagnosis occurs in the early stages, surgical treatment options may be successful.

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.

This type of melanoma can be harder to detect than others due to the symptoms occurring under the nails. Subungual melanoma is the most common type of melanoma among African American, Asian, and Hispanic people.

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.