• Typical age: Most patients are >50 years old; the median age at diagnosis is around 67 years.
• Gender: Slight male predominance (≈55 % of cases).
• Ethnicity: Predominantly affects fair‑skinned (Fitzpatrick I‑III) individuals.
• Prevalence: LM accounts for 5‑15 % of all melanomas in the United States, but up to 30 % of facial melanomas in older adults.^[1][2]

Symptoms

Because LM develops very slowly, many people mistake it for a harmless age spot. The following signs should raise suspicion:

Typical appearance

• Flat or slightly raised lesion with irregular borders.
• Color variation: shades of brown, tan, gray, or even black; often a “salt‑and‑pepper” pattern.
• Size: usually >5 mm; some lesions can enlarge to several centimeters over years.
• Location: most common on the nose, cheeks, forehead, ears, scalp, and dorsal hands.

Associated symptoms

• Itching or mild tenderness (rare).
• Occasional scaling or crusting.
• Gradual increase in size or change in color over months‑to‑years.

Any new, changing, or unevenly pigmented patch on sun‑exposed skin warrants evaluation.

Causes and Risk Factors

LM is not caused by a single factor but results from cumulative ultraviolet (UV) damage interacting with genetic susceptibility.

• Chronic UV exposure: Long‑term sunlight, especially intermittent intense exposure during youth and ongoing exposure in later life.^[3]
• Age: Risk rises after the fifth decade.
• Fair skin, red or blond hair, blue/green eyes: Less melanin offers less natural UV protection.
• History of sunburns or outdoor occupations: Farmers, construction workers, sailors.
• Personal or family history of melanoma or other skin cancers.
• Immunosuppression: Organ‑transplant recipients, HIV infection, or long‑term corticosteroid use.
• Genetic mutations: Alterations in the NRAS and CTNNB1 (β‑catenin) pathways have been identified in LM lesions.^[4]

Diagnosis

Early and accurate diagnosis is essential to prevent progression to invasive melanoma.

Clinical examination

• Dermatologist performs a thorough skin exam, focusing on sun‑exposed areas.
• Use of the ABCDE rule (Asymmetry, Border, Color, Diameter, Evolution) is modified for LM; “E” (Evolution) is especially important.

Dermatoscopy

Dermatoscopic patterns typical for LM include:

• Irregular pigmented follicular openings (“target” or “crown” pattern).
• Asymmetric pigmented rete ridges.
• Scattered dark gray dots and pepper‑like granules.

Biopsy

When LM is suspected, a tissue sample is required:

• Punch or excisional biopsy: Preferred to obtain full‑thickness epidermis.
• Incisional or shave biopsy: May miss deeper atypia; use only if lesion is very large.

Histopathology shows atypical melanocytes proliferating along the basal layer, with “pagetoid” upward spread but no dermal invasion.

Adjunctive tests

• Reflectance confocal microscopy (RCM): Non‑invasive, high‑resolution imaging useful for mapping lesion borders before surgery.
• Molecular testing: Gene expression profiling can aid in distinguishing LM from benign lentigines, though not routinely required.

Treatment Options

Treatment aims to eradicate atypical melanocytes while preserving cosmetic appearance, especially on the face.

Surgical excision

• Standard excision: 5‑mm clinical margin for LM in low‑risk sites; 10‑mm margin recommended on the head/neck.^[5]
• Mohs micrographic surgery (MMS): Provides the highest cure rate (~98 %) with tissue‑sparing margins; ideal for cosmetically sensitive areas.
• Wide local excision (WLE): May be used when MMS is unavailable.

Non‑surgical options

• Topical imiquimod 5 % cream: Immune response modifier applied once daily, 5‑times/week for 8‑12 weeks; success rates 70‑85 % in selected patients.^[6]
• Cryotherapy: Liquid nitrogen; useful for small lesions but higher recurrence.
• Radiation therapy: Considered for patients who cannot undergo surgery (e.g., poor surgical candidates).
• Photodynamic therapy (PDT): Less common; mixed evidence.

Follow‑up care

After treatment, most dermatologists recommend:

• Clinical skin exam every 3‑6 months for the first 2 years.
• Annual full‑body skin checks thereafter.
• Patient‑performed self‑exams monthly.

Living with Quasi‑malignant Melanoma (Lentigo Maligna)

Even after successful treatment, vigilance remains essential.

• Self‑examination: Use a mirror or ask a partner to check hard‑to‑see areas (nose, ears, scalp).
• Sun protection: Broad‑spectrum SPF 30+ sunscreen applied 15 minutes before exposure, reapplied every 2 hours.
• Protective clothing: Wide‑brimmed hats, UV‑protective sunglasses, and UPF clothing.
• Skin‑care routine: Gentle cleansing; avoid irritants that could obscure new lesions.
• Document lesions: Photographs with date stamps help track changes over time.
• Psychological support: Diagnosis can cause anxiety; consider counseling or support groups for skin‑cancer survivors.

Prevention

Because cumulative UV damage is the primary driver, primary prevention focuses on sun safety:

• Seek shade between 10 a.m. and 4 p.m.
• Apply broad‑spectrum sunscreen (SPF 30‑50) generously to face, scalp, and ears.
• Reapply after swimming, sweating, or towel‑drying.
• Wear UV‑blocking sunglasses and a wide‑brim hat.
• Avoid indoor tanning devices.
• Regular dermatologic skin checks for high‑risk individuals (fair skin, >50 years, personal/family melanoma history).

Complications

If LM is left untreated, it can progress to lentigo maligna melanoma (invasive melanoma), which carries the usual melanoma risks:

• Local tissue invasion: May lead to ulceration, bleeding, or secondary infection.
• Metastasis: Invasive melanoma can spread to lymph nodes, distant organs (lungs, liver, brain) and become life‑threatening.
• Cosmetic disfigurement: Larger, invasive lesions often require more extensive surgery.
• Psychological impact: Anxiety and reduced quality of life associated with a cancer diagnosis.

When to Seek Emergency Care

References

1. Mayo Clinic. “Lentigo maligna melanoma.” Accessed May 2024.
2. American Cancer Society. “Melanoma Skin Cancer Statistics,” 2023.
3. Centers for Disease Control and Prevention. “Sun Safety.” Updated 2023.
4. Jalili, R. et al. “Molecular pathways in lentigo maligna.” *Journal of Dermatologic Science*, 2022.
5. Cleveland Clinic. “Surgical margins for melanoma excision.” 2024.
6. Rastogi, S. et al. “Topical imiquimod for lentigo maligna: systematic review.” *Dermatologic Surgery*, 2021.