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When thinking about melanoma, many people envision moles and other dark skin spots. In most cases, this is accurate, but some relatively uncommon types of melanoma are completely colorless. Known as amelanotic melanomas, these skin lesions lack melanin, the dark pigment that gives most moles and melanomas their color. Instead, amelanotic melanomas can be clear, white or skin-colored, sometimes with a slight pink, purple or red tint.

Amelanotic melanoma is categorized as superficial spreading melanoma, which is the most common type of melanoma and accounts for approximately 70% of all cases. The cancer often originates in an existing mole and can develop anywhere on the body. Compared to melanomas with typical characteristics, amelanotic melanomas tend to be less noticeable and more likely to spread and recur.

Causes of—and risk factors for—amelanotic melanoma

Like all types of melanoma, amelanotic melanoma develops when certain skin cells (melanocytes) undergo abnormal changes that cause them to grow and divide very rapidly. The excess cells then build up, bind together and form tumors. The precise mechanisms behind the cellular mutations that lead to the development of skin cancer are not yet well understood.

Scientists do know that the primary risk factor for amelanotic melanoma is exposure to ultraviolet (UV) light from the sun and other sources, and the risk increases with the amount of exposure. Therefore, melanoma risk can be reduced by:

  • Not using indoor tanning beds, booths, lamps and other devices
  • Scheduling outdoor activities before 10 a.m. or after 4 p.m. because the sun’s rays are usually strongest during the midday hours
  • Using a broad-spectrum sunscreen with an SPF of at least 30, even on cloudy days
  • Reapplying sunscreen every two hours and immediately after swimming or perspiring
  • Wearing sun-protective clothing, such as pants and a long-sleeved shirt made of a dark, tightly woven fabric
  • Wearing sunglasses and a wide-brimmed hat

In addition to UV light exposure, other risk factors for amelanotic melanoma include:

  • A personal or family history of melanoma
  • A history of five or more blistering sunburns before age 20
  • More than 50 benign moles
  • Five or more atypical moles, which stand out from other moles due to their large size, color variations or indistinct borders
  • Fair skin or a complexion that does not tan easily and frequently burns
  • Skin with many freckles or a tendency to freckle after sun exposure
  • Blue or green eyes
  • Naturally red or blonde hair

Signs and symptoms of amelanotic melanoma

Because amelanotic melanomas lack pigment, they tend to be less noticeable than other melanomas. They are also more likely to be mistaken for a less serious form of skin cancer, such as basal cell carcinoma or squamous cell carcinoma, or a benign mole, cyst or scar. However, amelanotic melanomas often display other melanoma symptoms that are important to watch for, such as:

  • Asymmetry – If a line were to be drawn through the center of the lesion, the two halves would not match
  • Irregular borders – The edges of the lesion may be notched, scalloped or otherwise uneven
  • Evolution – Since the lesion first appeared, it may have changed in size, shape, color or elevation or started itching, bleeding or crusting

Another telltale sign of melanoma is an “ugly duckling,” a term that some physicians use to refer to a mole that stands out from the other moles on the body. This recognition strategy can be helpful because most benign moles on the body look alike.

Amelanotic melanomas tend to be diagnosed in advanced stages because they are often easily overlooked. To help ensure early detection of any type of skin cancer, The Skin Cancer Foundation recommends a monthly head-to-toe skin check for new moles as well as changes in existing moles. Any unusual skin changes should promptly be discussed with a dermatologist. This is important because early-stage melanomas are highly treatable and can often be cured.

Diagnosing amelanotic melanoma

As with most types of cancer, a conclusive diagnosis of amelanotic melanoma requires a biopsy. After applying a local anesthetic, a physician will carefully remove all or as much as possible of the suspicious skin growth, then send it to a lab for a microscopic examination by a dermatopathologist.

If the dermatopathologist identifies cancerous cells in the removed tissue, they will note details on the thickness of the lesion, any loss of surface skin (ulceration), the rate of cell division (mitotic rate) and whether any immune cells (tumor-infiltrating lymphocytes) are identified. Along with imaging scans, such as computed tomography (CT), magnetic resonance imaging (MRI) and/or ultrasounds scans, this information can help a physician determine the extent and spread of the cancer, then assign a stage and plan treatment.

Amelanotic melanoma treatment

Like all forms of melanoma, amelanotic melanoma is treated based on its stage, location and symptoms. Many patients benefit from a combination of therapies, such as:

  • Surgery – A wide excision can be performed to remove the cancerous lesion and a slim margin of surrounding healthy tissue. If needed, the surgical session may include a skin graft. If the cancer has spread to nearby lymph nodes, a lymph node dissection may also be performed.
  • Radiation therapy – External beam radiation therapy (EBRT) involves generating high-energy X-rays from a source outside the body and precisely targeting those rays at the cancerous tissues. EBRT may be considered if the cancer cannot be surgically removed or has spread to the bones, and also to help prevent a recurrence after surgery.
  • Immunotherapy – Medications are delivered to augment the body’s immune system and boost its natural ability to fight cancer.
  • Targeted therapy – Medications are used to inhibit the effectiveness of the specific tissue environment, genes or proteins that are allowing the cancer to thrive and grow.

If there are multiple amelanotic melanomas on a single limb, isolated limb infusion therapy may be used to deliver chemotherapy only to the affected limb. On the other hand, traditional chemotherapy may be considered to address widespread cancer.

The Moffitt Cancer Center difference for amelanotic melanoma

A National Cancer Institute-designated Comprehensive Cancer Center, Moffitt Cancer Center is home to a compassionate team of experts who specialize in researching and treating all forms of melanoma, including amelanotic melanoma. Our Cutaneous Oncology Program is led by world-class physician-researchers who ensure that each patient’s treatment plan is individualized, comprehensive and coordinated. We follow each patient’s progress and finetune their treatment as appropriate, and we are continually investigating and developing novel ways to enhance our patients’ experience and quality of life. Through ongoing research, we have dramatically improved the outlook for people with melanoma through innovative treatments, such as immunotherapy and targeted therapy, and we make further progress every day.

If you would like to discuss your skin cancer symptoms with a melanoma specialist in our Cutaneous Oncology Program, you can request an appointment by calling 1-888-663-3488 or submitting a new patient registration form online. As Florida’s top cancer hospital, we are changing the model, and we will connect you with a cancer expert as soon as possible.