Identifying Subungual Melanoma

Potentially deadly nail cancer is often misdiagnosed

Wrinkled hands as it's important to examine your hands for a subungual melanoma
What is a subungual melanoma, what symptoms should you be aware of, and how are they treated?. Nurcholis Anhari Lubis / Stringer / Getty Images

Subungual melanoma, also referred to as cancer of the nail unit, is a type of malignancy which arises in the tissues of the nail bed. A melanoma is a type of cancer that develops in cells called melanocytes. Melanocytes are cells that produce melanin, the pigment that gives skin, hair, and eyes their color.

While subungual melanomas are most commonly found on the thumb or big toe, they can occur on any of the fingernails or toenails.

They are often misdiagnosed as a fungal infection due to their characteristic changes in color and nail texture.

Subungual melanoma is a relatively uncommon condition and tends to occur more in darker-skinned individuals. In Asia, it is thought that as many as 20 percent of melanomas are subungual melanomas. They occur most often in people between the ages of 40 and 70.

Symptoms of Subungual Melanoma

Subungual melanomas usually appear as a darkened streaks that run longitudinally (perpendicular to the cuticle). Roughly half of these streaks are brown, blue, or black, while the other half are non-pigmented.

As the cancer progresses, more streaks may appear, often with different colors. As time progresses, the portion closest to the cuticle may become wider.

Hutchinson's sign is a common finding in most subungual melanomas. This refers to the appearance of a streak extending from to the top of the nail all the way to the nail bed (where the nail begins) and into the cuticle itself.

This differentiates it from other nail-related conditions in terms of its uniformity, longitudinal discoloration, and involvement of the cuticle.

As the melanoma continues to grow, it can cause bleeding, the formation of a nodule, or deformity to the nail itself.

Diagnosis of Subungual Melanoma

A diagnosis of will usually made with careful inspection of the nail and lesion.

Dermatologists will use a tool called a dermascope which provides them a magnified view of the nail and surrounding tissue.

Ultimately, a visual examination has its limitations, especially since it so infrequently seen. As a result, it is often mistaken for other, more common conditions, such as:

  • subungual hematoma, a bruising beneath the nail which lacks the uniformity of subungual melanoma
  • fungal infections (onychomycosis) which more often have dark, non-longitudinal stripes accompanied by yellow or white streaks
  • moles (nevi) which are less likely to appear in streaks
  • deposits of melanin beneath the nail which can occur as a result of pregnancy (as well as chemotherapy or radiation therapy)

A definitive diagnosis can only be made with a biopsy (the removal and examination of affected tissue).

If a melanoma is suspected, an excisional biopsy will usually be performed to remove the entire lesion plus some of surrounding tissue. A less-invasive punch or incisional biopsy may be used if the visual diagnosis is less conclusive.

Staging of Melanoma

Depending on the size and depth of a subungual melanoma, further testing will be needed to determine the stage of the disease. As with other forms of cancer, the stage can vary from carcinoma in situ (precancer) all the way to stage 4 metastatic disease (where the cancer has spread to other organs).

To determine whether the melanoma has metastasized, there are various tests the oncologist can turn to including the biopsy of sentinel lymph nodes (the nodes nearest the tumor) and imaging techniques such as computerized tomography (CT scan) or positron emission tomography (PET scan).

Risk Factors of Subungual Melanoma

While we still don’t know what causes subungual melanoma, we do know many of the risk factors associated with its development.

The one thing that doesn’t appear to be a factor — and differentiates it from all other types of melanoma — is sun exposure. Ultraviolet (UV) radiation from the sun or other sources neither contributes to its development nor enhances the speed by which it develops.

The risk factors that do play a part include:

  • previous trauma to the fingers or toes (a common finding)
  • personal or family history of melanoma
  • multiple moles
  • immune suppression, including organ recipients and people with advanced HIV
  • genetics, such as those with the hereditary condition xeroderma pigmentosa (extreme sensitivity to UV radiation)

Treatment of Subungual Melanoma

The treatment of subungual melanomas has changed considerably in recent years. In the past, amputation of the entire toe or finger was considered the treatment of choice.

Today, many subungual melanomas are treated more conservatively with only the local removal of the tumor. When amputation is indicated, it often involves only the first joint nearest the fingernail. For toenails, amputation to the second joint is more common.

A 2014 review of medical literature suggested that a more conservative approach may work just as well as a complete amputation; moreover, complete amputation was not shown to improve survival.

For advance subungual melanoma, other types of therapy may be needed, including:

  • chemotherapy, given either systemically through a vein or directly into the tumor
  • radiation therapy, used primarily as a palliative treatment to decrease pain
  • immunotherapy, a newer form of cancer therapy that aims to stimulate the immune system to fight cancerous cells
  • targeted therapies, drugs able to target the BRAF mutations that occur in 50 percent of subungual melanoma tumors

Response to treatment can vary based largely on the stage of the cancer. Outcomes for people with subungual melanoma tend to poorer than other types of melanoma, often due to delay in seeking diagnosis and treatment.

This only highlights the need for action should you find any changes to the nail or skin that seem abnormal or fail to get better. Early intervention is the surest way to achieve treatment success.

A Word From Verywell

If you've been diagnosed with subungual melanoma, it's important to find a specialist experienced with the disease. Subungual melanomas are fairly uncommon, and the lack of experience can result in an unnecessarily aggressive approach to treatment.

While having an excellent care team around you is important, ​you remain the most important facet of that team. Learn as much as you can about your cancer. Ask for help and accept help. Become involved with online support communities who can share their experiences and insights.

And make a point of becoming your own advocate in your cancer care. It really does make a difference.

Sources:

Cochran, A.; Buchanan, P.; Bueno, R.; et al. "Subungual Melanoma: A Review of Current Treatment." Plastic and Reconstructive Surgery. 2014; 134(2):259-73.

Nguyen, J.; Bakri, K.; Nguyen, E.; et al. "Surgical Management of Subungual Melanoma: Mayo Clinic Experience of 124 Cases." Annals of Plastic Surgery. 2013; 71(4):346-54.

Ohn, J.; Choe, Y.; Park, J.; et al.  "Dermoscopic Patterns of Fungal Melanoychia: A Comparative Study with other Causes of Melanonychia." Journal of the American Academy of Dermatology. October 25, 2016 (Epub ahead of print).

Continue Reading