Melanomas are a type of cancera disease where abnormal cells split without control and spread to other nearby body tissue and/or organs that develop from melanocytes, which are the cellsthe basic structural and functional unit of all living things that produce pigment, generally in the skin. However, they can also develop in the eye and possibly other parts of the body. Nail unit melanomaa type of cancer that develops from melanocytes, which are the cells that produce pigment generally in the skin (but can develop in other areas of the body) is a rare variant of cutaneous melanoma (or melanoma of the skin) which develops underneath the fingernail.
The nail is composed of four main structures: nail plate, nail matrix, nail bed, and periungual soft tissues. The nail plate, also known as the nail body, is the protective outer visible layer of the nail that is made up of hardened, tightly packed keratin cells. The nail plate is produced by the nail matrix, which sits at the base of the nail. The nail bed is the pink, soft tissues that lie beneath the nail plate that contains the nerves and bloodthe red bodily fluid that transports oxygen and other nutrients around the body vessels required for nail growth. Periungual soft tissues, including the eponychium (cuticle), nail folds, and hyponychium, are supportive tissues surrounding the nail that provide support and protection to the nail.
In most cases, a nail unit melanoma develops in the nails of the thumb or the big toe. However, it can develop in any nails of the fingers and toes.
Nail unit melanoma tends to be diagnosed equally among the sexes, and is most common in people between the ages of 50-70. However, anyone can develop this disease at any age.
Types of Nail Unit Melanoma
There are three primary types of nail unit melanoma which are classified by the types of cells they develop from.
Subungual Melanoma
Subungual melanomas are the most common type of nail unit melanoma, and they develop from the nail matrix portion of the nail. These cancers are often associated with trauma, and therefore are often diagnosed at a late stage of disease. Subungual melanomas can be aggressive, but can have a good prognosisto predict how a disease/condition may progress and what the outcome might be when caught early.
Ungual Melanoma
Ungual melanomas are a less common subtype of nail unit melanomas, and they develop from underneath the nail plate. These cancers are often associated with trauma, and therefore are often diagnosed at a late stage of disease. Ungual melanomas can be aggressive, but can have a good prognosis when caught early.
Periungual Melanoma
Periungual melanomas are a less common subtype of nail unit melanomas that develop from the periungual soft tissues surrounding the nail. These cancers are often associated with trauma, and therefore are often diagnosed at a late stage of disease. Periungual melanomas can be aggressive, but can have a good prognosis when caught early.
Treatment
If a nail unit melanoma is detected, it will be staged and graded based on size, metastasiswhen the cancer has spread to other parts of the body, also known as mets, and how the cancer cells look under the microscope. Stagingthe process of determining how big the cancer is, where it started and if it has spread to other areas and grading helps your doctors determine the best treatment for you.
Cancers can be staged using the TNM staging system:
- T (tumoura tissue mass that forms from groups of unhealthy cells) indicates the size and depth of the tumour.
- N (nodea small lump or mass of tissue in your body) indicates whether the cancer has spread to nearby lymph nodessmall bean-shaped structures that filters harmful substances from lymph fluid.
- M (metastasis) indicates whether the cancer has spread to other parts of the body.
This system can also be used in combination with a numerical value, from stage 0-IV:
- Stage 0: this stage describes cancer cells in the place of origin (or ‘in situ’) that have not spread to nearby tissuea group of cells that work together to perform a function.
- Stage I: cancer cells have begun to spread to nearby tissue. It is not deeply embedded into nearby tissue and had not spread to lymph nodes. This stage is also known as early-stage cancer.
- Stage II: cancer cells have grown deeper into nearby tissue. Lymph nodes may or may not be affected. This is also known as localisedaffecting only one area of body cancer.
- Stage III: the cancer has become larger and has grown deeper into nearby tissue. Lymph nodes are generally affected at this stage. This is also known as localised cancer.
- Stage IV: the cancer has spread to other tissues and organs in the body. This is also known as advancedat a late stage, far along or metastatic cancer.
Cancers can also be graded based on the rate of growth and how likely they are to spread:
- Gradea description of how abnormal cancer cells and tissue look under a microscope when compared to healthy cells I: cancer cells present as slightly abnormal and are usually slow growing. This is also known as a low-grade tumour.
- Grade II: cancer cells present as abnormal and grow faster than grade-I tumours. This is also known as an intermediate-grade tumour.
- Grade III: cancer cells present as very abnormal and grow quickly. This is also known as a high-grade tumour.
Once your tumour has been staged and graded, your doctor may recommend genetic testinga procedure that analyses DNA to identify changes in genes, chromosomes and proteins, which can be used to analyse tumour DNA to help determine which treatment has the greatest chance of success, which analyses your tumour DNA and can help determine which treatment has the greatest chance of success. They will then discuss the most appropriate treatment option for you.
Treatment is dependent on several factors, including location, stage of disease and overall health.
Treatment options for nail unit melanomas may include:
- Surgerytreatment involving removal of cancerous tissue and/or tumours and a margin of healthy tissue around it to reduce recurrence, potentially including:
- Wide local excisionremoval of cancerous tissue and a margin of healthy tissue around it to prevent cancer recurrence of the tumour.
- Mohs micrographic surgeryspecialised surgery that removes thin layers of cancer in stages until completely removed.
- Lymphadenectomysurgical removal of lymph node(s).
- Amputationcomplete or partial removal of a limb of affected finger or toe (in rare cases).
- Chemotherapya cancer treatment that uses drugs to kill or slow the growth of cancer cells, while minimising damage to healthy cells.
- Radiation therapya treatment that uses controlled doses of radiation to damage or kill cancer cells.
- Immunotherapya treatment that uses a person's immune system to fight cancer.
- Targeted therapymedication that targets specific molecular features of cancer cells.
- Clinical trialsresearch studies performed to test new treatments, tests or procedures and evaluate their effectiveness on various diseases.
- Palliative carea variety of practices and exercises used to provide pain relief and improve quality of life without curing the disease.
Risk factors
While the cause of nail unit melanoma remains unknown, the following factors may increase the riskthe possibility that something bad will happen of developing the disease:
- Certain genetic mutations.
- Family and/or personal history of melanoma.
- Being of African, Japanese, Chinese, and/or Native American heritage.
Unlike most melanomas, UV exposure has not been identified as a risk factor of this disease.
Not everyone with these risk factors will develop the disease, and some people who have the disease may have none of these risk factors. See your general practitioner (GP) if you are concerned.
Symptoms
Symptoms of a nail unit melanoma may include:
- A narrow brown-black band that extends the length of the nail.
- Irregular borders of bands in nail.
- Hutchinson sign (band extends into skin surrounding the nail).
- Nodulation, ulceration and/or bleeding of lesion.
- A massa growth of cells that come together to make a lump, may or may not be cancer under the nail plate.
- Thinning, cracking, and/or distortion of the nail plate.
- Painful lesion.
ABCDEF of Nail Unit Melanoma
To assist in the assessment of a suspected nail unit melanoma, physicians have made up an ABCDEF mnemonic:
- A – Age (50-70); African, Japanese, Chinese, and/or Native American heritage.
- B – Brown-black pigmented band that is greater than 3 millimetres and blurred borders.
- C – Change or lack of change despite treatment of nail band or lesion.
- D – Digit most commonly involved (big toe and thumb).
- E – Extension of pigment into skin surrounding the nail (also known as Hutchinson sign).
- F – Family or personal history of melanoma.
Not everyone with the symptoms above will have cancer, but see your general practitioner (GP) if you are concerned.
Diagnosis
If your doctor suspects you have a nail unit melanoma, they may order the following tests to confirm the diagnosisthe process of identifying a disease based on signs and symptoms, patient history and medical test results and refer you to a specialist for treatment:
- Physical examinationan examination of your current symptoms, affected area(s) and overall medical history.
- Biopsyremoval of a section of tissue to analyse for cancer cells.
