Acral Lentiginous Melanoma: Symptoms, Causes, Diagnosis, Treatment, and Prognosis
~Introduction to Acral Lentiginous Melanoma
Acral Lentiginous Melanoma (ALM) is a rare but highly aggressive subtype of melanoma skin cancer that develops on the palms of the hands, soles of the feet, or beneath the fingernails and toenails. Unlike most melanomas, acral lentiginous melanoma is not linked to sun exposure, making it more difficult to detect and often misunderstood by both patients and healthcare providers.
Although ALM represents a small percentage of melanoma cases overall, it is associated with higher mortality rates due to delayed diagnosis and advanced disease at presentation. Alarmingly, acral lentiginous melanoma is the most common type of melanoma in people with darker skin tones, including individuals of African, Asian, and Hispanic descent.
This SEO-optimized article provides a comprehensive overview of acral lentiginous melanoma, covering symptoms, causes, risk factors, diagnosis, staging, treatment options, prognosis, and prevention strategies.
~What Is Acral Lentiginous Melanoma?
Acral lentiginous melanoma is a malignant tumor of melanocytes, the pigment-producing cells of the skin. The term acral refers to peripheral body parts (hands, feet, nails), while lentiginous describes the pattern of cancer cell growth along the basal layer of the epidermis.
Key Characteristics of ALM
Develops on palms, soles, and nail beds
Occurs in non–sun-exposed areas
Grows slowly at first but becomes aggressive
Often diagnosed at advanced stages
Affects all skin types equally
~Epidemiology of Acral Lentiginous Melanoma
How Common Is Acral Lentiginous Melanoma?
Acral lentiginous melanoma accounts for approximately:
2–3% of melanomas in Caucasian populations
30–50% of melanomas in Asian populations
Up to 60% of melanomas in Black populations
Despite similar overall melanoma incidence rates across races, mortality is higher in darker-skinned individuals, largely due to late diagnosis of ALM.
Age and Gender Distribution
Most commonly diagnosed between 50 and 70 years of age
Slight male predominance
Rare but possible in younger individuals and children
~Causes and Risk Factors of Acral Lentiginous Melanoma
What Causes Acral Lentiginous Melanoma?
The exact cause of acral lentiginous melanoma remains unclear. Unlike other melanoma types, ultraviolet (UV) radiation is not a major risk factor.
Known and Suspected Risk Factors
Genetic mutations (KIT, NRAS, BRAF)
Chronic mechanical stress or trauma to hands and feet
Older age
Personal or family history of melanoma
Immunosuppression
Importantly, skin pigmentation does not protect against ALM, highlighting the need for awareness in all populations.
~Molecular and Genetic Features
Acral lentiginous melanoma is genetically distinct from sun-related melanomas.
Common Genetic Alterations
KIT mutations or amplifications
NRAS mutations
Lower frequency of BRAF mutations
Extensive chromosomal abnormalities
These molecular differences influence treatment decisions and explain variable responses to standard melanoma therapies.
~Symptoms of Acral Lentiginous Melanoma
Why ALM Is Often Missed
ALM develops in areas people rarely examine closely. Early lesions may be painless and resemble benign conditions such as bruises, calluses, or fungal infections.
Early Signs and Symptoms
Flat, irregular dark patch on palms or soles
Uneven pigmentation (brown, black, gray)
Asymmetrical lesion
Slow growth over months or years
Advanced Symptoms
Raised or nodular lesion
Ulceration or bleeding
Pain or tenderness
Thickened or cracked skin
Nail splitting or destruction
Subungual Acral Lentiginous Melanoma (Nail Melanoma)
Dark streak under the nail
Pigmentation spreading to surrounding skin (Hutchinson sign)
Nail lifting or breaking
Often mistaken for trauma or infection
~Diagnosis of Acral Lentiginous Melanoma
Clinical Examination
Diagnosis begins with a thorough examination of the hands, feet, and nails. Traditional melanoma screening tools like the ABCDE rule are less effective for ALM.
Modified ABCDE for ALM
A – Asymmetry
B – Border irregularity
C – Color variation
D – Diameter >7 mm
E – Evolution or change
Dermoscopy
Dermoscopy improves early detection and may reveal:
Parallel ridge pattern (highly suggestive of ALM)
Irregular pigmentation
Asymmetric structures
Biopsy
A biopsy is required for definitive diagnosis:
Excisional biopsy (preferred)
Punch or incisional biopsy for large lesions
Nail matrix biopsy for subungual lesions
Histopathology Findings
Lentiginous proliferation of atypical melanocytes
Pagetoid spread
Dermal invasion in advanced cases
~Staging of Acral Lentiginous Melanoma
ALM is staged using the American Joint Committee on Cancer (AJCC) melanoma staging system, based on:
Tumor thickness (Breslow depth)
Ulceration
Lymph node involvement
Distant metastasis
Common Stage at Diagnosis
Due to delayed detection, many patients present with Stage II or Stage III disease, significantly affecting prognosis.
~Treatment Options for Acral Lentiginous Melanoma
Surgical Treatment
Surgery is the primary treatment for localized disease.
Wide local excision with appropriate margins
Sentinel lymph node biopsy
Partial or complete digit amputation in nail melanoma cases
Adjuvant Therapy
Depending on stage and risk factors:
Immunotherapy (PD-1 inhibitors)
Targeted therapy for actionable mutations
Radiation therapy for local control
Treatment for Advanced or Metastatic ALM
Combination immunotherapy
Targeted molecular agents
Palliative radiation
Enrollment in clinical trials
ALM often responds less favorably to therapy than cutaneous melanoma, emphasizing early detection.
~Prognosis and Survival Rates
Overall Prognosis
Acral lentiginous melanoma has a worse prognosis compared to other melanoma subtypes.
Survival Statistics (Approximate)
Stage I: 80–90% 5-year survival
Stage II: 50–70%
Stage III: 30–50%
Stage IV: <20%
Prognostic Factors
Tumor thickness
Ulceration
Lymph node involvement
Speed of diagnosis
Response to systemic therapy
~Prevention and Early Detection
Can Acral Lentiginous Melanoma Be Prevented?
There are no guaranteed prevention strategies, but early detection dramatically improves survival.
Self-Examination Tips
Inspect palms, soles, and nails monthly
Use mirrors or assistance
Look for new or changing lesions
Do not ignore nail discoloration
Clinical Screening
Regular dermatologic exams for high-risk individuals
Increased awareness among healthcare providers
Prompt biopsy of suspicious acral lesions
~Research and Future Directions
Emerging Therapies
Novel immunotherapy combinations
Precision medicine based on genetic profiling
AI-assisted dermoscopy for early detection
Improved targeted therapies for KIT mutations
Clinical Trials
Because ALM is rare and aggressive, clinical trial participation is strongly encouraged to improve outcomes and advance research.
~Living With Acral Lentiginous Melanoma
A diagnosis of ALM can be emotionally challenging. Comprehensive care should include:
Multidisciplinary oncology teams
Psychological counseling
Pain and symptom management
Patient education and support groups
~Conclusion
Acral lentiginous melanoma is a rare but deadly form of melanoma that often goes undetected until advanced stages. Its occurrence in non–sun-exposed areas and higher prevalence among people with darker skin tones highlight the urgent need for awareness and education.
Early recognition, prompt biopsy, and advances in immunotherapy and targeted treatments offer hope for improved survival. Regular self-examination of the hands, feet, and nails—combined with professional screening—remains the most effective strategy for reducing mortality from this overlooked cancer.
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