- Acral melanoma is a rare form of skin cancer that occurs on the extremities, specifically the palms, soles of the feet, and under the nails.
- Unlike conventional melanoma caused by UV radiation, the exact cause of acral melanoma remains unknown, though local trauma is a hypothesis.
- The primary danger lies in its ability to mimic benign conditions such as granulomas, hematomas, fungal infections, and warts.
- Because these lesions often do not cause pain or itching in early stages, both patients and physicians may overlook the possibility of malignancy.
Quick Summary
Acral melanoma is a rare subtype of skin cancer that develops on the palms, soles of the feet, and beneath the nails. Unlike common melanomas associated with sun exposure, this type appears on extremities and often presents as a pigmented lesion that can easily be mistaken for benign conditions like bruises, warts, or fungal infections.
The primary challenge with acral melanoma is the delay in diagnosis. Because these lesions typically do not cause pain, itching, or bleeding in their initial stages, they are frequently misidentified. This confusion leads to the application of incorrect treatments, such as cauterization, which can destroy the tissue necessary for determining the cancer's thickness and prognosis. Experts emphasize that early diagnosis is critical, as the prognosis worsens significantly if the cancer is allowed to progress due to mistaken identity. Treatment generally involves surgery, with modern techniques focusing on preserving the affected digit whenever possible.
Understanding Acral Melanoma
Acral melanoma is defined by its location on the body's extremities. The term "acral" refers to the distal parts of the limbs, specifically the hands and feet. This type of cancer originates from the transformation of melanocytes, the cells responsible for producing melanin, the pigment that gives skin its color.
While conventional melanoma is often linked to ultraviolet radiation exposure, acral melanoma behaves differently. It typically manifests in the following areas:
- The plantar surface (soles of the feet)
- The palmar surface (palms of the hands)
- Subungual regions (under the fingernails or toenails)
Despite its low incidence compared to other skin cancers, acral melanoma poses a significant threat due to its deceptive appearance. In its early stages, the lesion often lacks symptoms such as pain, itching, or bleeding, which contributes to it being overlooked.
When the melanoma is cauterized, we lose fundamental information for the prognosis, such as its thickness, which guides the treatment and follow-up of the patient.— Luiz Fernando Nunes, Surgical Oncologist
The Danger of Misdiagnosis 🩺
The most critical issue regarding acral melanoma is its ability to disguise itself as a benign condition. Because it appears on extremities, it is frequently confused with common ailments that affect these areas. This confusion leads to a delay in the correct diagnosis and the start of appropriate treatment.
According to medical experts, acral melanoma is often mistaken for:
- Granulomas (often described as "spongy flesh")
- Hematomas (bruises or blood blisters)
- Verrucas (warts)
- Onychomycosis (fungal infections of the nail)
The risk intensifies when a physician, suspecting a benign condition, initiates treatment without a definitive diagnosis. For instance, cauterization (burning the tissue) is a common procedure for benign lesions. However, if applied to a melanoma, it can be disastrous. As noted by specialists, cauterizing a cancerous lesion may make the surface appear healed while the tumor continues to grow internally. Furthermore, this process destroys the tissue, removing vital information regarding the tumor's thickness—a key factor in determining the prognosis and treatment plan.
Diagnosis and Treatment Options
Accurate diagnosis of acral melanoma requires a systematic approach starting with clinical suspicion. If a patient notices a new spot on the palm or sole, or a dark stripe under a nail, they should seek medical evaluation immediately. Even lesions that appear granulomatous or verrucous should be treated with caution.
The diagnostic process typically follows these steps:
- Dermatoscopy: An examination using a special magnifying lens to view structures not visible to the naked eye. This helps differentiate between benign and malignant lesions.
- Biopsy: A sample of the tissue is taken for anatomopathological examination. This can be excisional (removing the whole lesion) or incisional (removing a part of it).
- Anatomopathological Analysis: The pathologist confirms the diagnosis and assesses key prognostic factors.
Once confirmed, the pathology report provides essential data for surgical planning. This includes the Breslow thickness (depth of the lesion in millimeters), the presence of ulceration, the mitotic index (speed of cell division), and angiolymphatic invasion.
Surgery is the primary treatment. In the past, melanoma under the nail often resulted in amputation of the finger. However, recent studies have shown that digit preservation is possible in early cases without compromising survival rates or increasing recurrence. This functional surgery maintains both the aesthetics and functionality of the digit. In advanced cases where metastasis has occurred, treatments may include immunotherapy, targeted therapy, chemotherapy, and radiation.
Risk Factors and Prevention
Unlike cutaneous melanoma (the conventional type affecting the face, scalp, and trunk), the exact cause of acral melanoma is not well defined. It is not associated with UV radiation exposure. Instead, the leading hypotheses point toward local trauma or mechanical stress as potential triggers.
Because the central risk factor is not established, primary prevention (preventing the disease from starting) is currently impossible. Therefore, the medical focus shifts entirely to secondary prevention. This involves early diagnosis, which offers the patient a chance for a cure through simple lesion removal. Regular self-examination of the hands and feet is crucial for identifying changes in existing moles or the appearance of new pigmented lesions.
"Imagine what can happen if you 'burn' a cancer: the lesion may look better on the outside, but the tumor continues to evolve."
— Luiz Fernando Nunes, Surgical Oncologist
Frequently Asked Questions
What is acral melanoma?
Acral melanoma is a rare type of skin cancer that occurs on the extremities, specifically the palms of the hands, soles of the feet, and under the nails.
Why is acral melanoma often diagnosed late?
It is often diagnosed late because it mimics benign conditions like bruises or warts, and it usually does not cause pain or itching in early stages, leading to a delay in seeking medical attention or performing a biopsy.
How is acral melanoma treated?
The primary treatment is surgery. In early cases, functional surgery can preserve the digit, avoiding amputation. In advanced cases, therapies like immunotherapy or chemotherapy may be used.
