What are the recommended steps for a 30-year-old white male with a 5-month history of a lesion on the sole of his foot, considering the risk of melanoma, particularly acral lentiginous melanoma?

Melanoma Risk Assessment and Management for Acral Lesion

Immediate Action Required

This 30-year-old white male with a 5-month persistent lesion on the sole of his foot requires urgent referral to a dermatologist or surgeon with expertise in pigmented lesions, to be seen within 2 weeks, as acral lentiginous melanoma (ALM) must be excluded. 1, 2, 3

Why This is High Priority

• Acral lentiginous melanoma is a distinct and aggressive melanoma subtype that occurs on palms, soles, and subungual sites, characterized by slow radial growth initially but with potential for rapid vertical growth and early metastatic spread 4, 5, 6

• While ALM is less common in white populations compared to Asian or African descent patients, any persistent pigmented lesion on acral sites (palms, soles, nail beds) warrants immediate evaluation regardless of race 1, 4, 6

• The 5-month duration is concerning because ALM is frequently diagnosed at late stages due to delays in recognition, and lesions are typically unusually large, thick, and ulcerated at diagnosis 4, 5, 6

• ALM has worse prognosis than other melanoma subtypes when diagnosed late, with 5-year survival for plantar lesions at 63% for Stage I disease, dropping to 27% for digital skin lesions 4

Clinical Assessment Features to Document

The specialist should evaluate for these specific ALM characteristics:

• Asymmetry, border irregularities, color heterogeneity, and evolution in size/appearance (ABCD criteria) 1, 3

• Size and thickness of the lesion, as ALM lesions are characteristically large at presentation 4, 5

• Presence of ulceration, which is common in ALM and affects prognosis 4, 5

• Complete skin examination including all acral sites, regional lymph nodes, and assessment for satellites or in-transit metastases 1, 3

• Dermoscopy by an experienced physician significantly enhances diagnostic accuracy for pigmented lesions 1, 7

Biopsy Approach

Full-thickness excisional biopsy is mandatory and is the only acceptable diagnostic approach:

• Include the entire lesion with a 2-5 mm clinical margin of normal skin and a cuff of subdermal fat to allow accurate Breslow thickness measurement 1, 2, 3

• Shave and punch biopsies are absolutely contraindicated as they make pathological staging impossible and lead to sampling error 1, 2, 3

• Incisional biopsy is occasionally acceptable for acral melanoma when performed by specialists within a skin cancer multidisciplinary team, but only when complete excision is impractical 1

• The biopsy should be oriented to facilitate subsequent wide local excision if melanoma is confirmed 1

Required Histopathology Information

The pathology report must include:

• Breslow thickness in millimeters (critical for staging and determining surgical margins) 1, 3

• Presence and extent of ulceration (affects staging and prognosis) 1, 3

• Mitotic rate (prognostic value, especially for thin melanomas) 1

• Surgical margin clearance status 1, 3

• Melanoma subtype confirmation (acral lentiginous vs. other types) 1

• Presence and extent of regression (common in ALM and affects treatment decisions) 5

Definitive Treatment Based on Diagnosis

If melanoma in situ (lentigo maligna) is confirmed:

• Surgical excision with 0.5 cm margins is standard 1, 2

If invasive melanoma is confirmed, margins depend on Breslow thickness:

• <1 mm depth: 1 cm margin 1, 2
• 1-2 mm depth: 1-2 cm margin (2 cm preferred where functionally feasible) 1, 2
• >2 mm depth: 2 cm margin 1, 2

For subungual melanomas >1 mm or showing vertical growth phase:

• Amputation of the digit with lymph node dissection is recommended 5

For lesions with severe regression or measuring >1 mm:

• Wide local excision with lymph node dissection should be considered 5

Sentinel Lymph Node Biopsy Considerations

• SLNB should be discussed for lesions ≥0.8-1.0 mm thickness or thinner lesions with adverse features (ulceration, high mitotic rate) 1

• Patients with lymph node metastases at diagnosis have significantly shorter survival (P = 0.027) 5

Critical Pitfalls to Avoid

• Do not delay referral – ALM progresses rapidly and early metastatic spread is common 6, 8

• Do not perform partial biopsies in primary care – this leads to sampling error and missed diagnoses 1, 2

• Do not underestimate acral lesions in white patients – while less common than in other populations, ALM occurs in all races 1, 4

• Do not assume benign diagnosis without biopsy – any persistent acral lesion requires histologic confirmation 1, 3

• Anatomic peculiarities of acral sites make Clark level determination difficult, emphasizing the need for experienced pathology review 5