eMedicine Specialties > Oncology > Carcinomas of the Skin

Lentigo Maligna Melanoma

Author: Winston W Tan, MD, Assistant Professor of Medicine, Mayo Medical School; Consulting Staff, Mayo Group Practices
Coauthor(s): Antony J Charles, MD, Fellow, Department of Hematology and Oncology, Mayo Clinic, St Luke's Hospital; Broc L Pratt, MD, Consulting Staff, Metrolina Plastic Surgery, Charlotte, North Carolina; B Todd Heniford, MD, Assistant Clinical Professor, Department of General Surgery, University of North Carolina; Chief, Division of Minimal Access Surgery, Carolinas Medical Center
Contributor Information and Disclosures

Updated: Mar 4, 2009

Introduction

Background

The overall incidence of cutaneous melanoma (skin cancer) is increasing faster than that of any other neoplasm. In 2006 and 2007, approximately 60,000-62,000 new cases of invasive skin melanoma and more than 48,000 in situ melanomas were diagnosed.^1,2

Lentigo maligna (LM) is a subtype of melanoma in-situ. Lentigo maligna melanoma (LMM) is one of the 4 main subtypes of invasive melanoma and represents 5-15% of cases. The other types are superficial spreading (70%), nodular (10-15%), and acral lentiginous melanoma (5%).³

Lentigo maligna melanoma is most often found in the head and neck. Approximately 10-30% of all cutaneous melanoma arise in this region.

Sir John Hutchinson first described lentigo maligna in 1890; the disease continues to be called Hutchinson melanotic freckle on occasion. The Hutchinson melanotic freckle was originally thought to be infectious because of its slow yet progressive growth. The lesion has subsequently been characterized as malignant lentigo of elderly people, junctional nevus, and melanoma in situ. Most authors currently refer to it as lentigo maligna when it is confined to the epidermis and lentigo maligna melanoma when it violates the dermis.

See also Malignant Melanoma.

Pathophysiology

Many authors consider lentigo maligna to be a preinvasive lesion induced by long-term cumulative ultraviolet injury. Conceptually, the term melanoma is used when atypical melanocytes invade the rich vascular and lymphatic networks of the dermis, thereby establishing metastatic potential.

Most malignant melanomas arise as superficial tumors confined to the epidermis, which is often known as horizontal growth. At some point, a stepwise accumulation of genetic abnormalities leads to proliferation and progression to the vertical growth phase, which leads to dermal and deeper involvement and subsequently nodal metastases.

See related CME at Predictors of Rapid Growth Identified for Melanomas.

Frequency

United States

For all types of melanoma, in the United States, the American Cancer Society projects that 62,480 (34,950 male and 27,530 female) new cases will be diagnosed in 2008. They predict that 8,420 (5,400 male and 3,020 female) deaths will occur in 2008 attributable to melanoma.^4,5

The incidence of lentigo maligna is greatest in Hawaii, intermediate in the central and southern states, and lowest in the northern states.

International

The incidence of melanoma is highest in Australia, where lentigo maligna can be found at an annual rate of 1.3 cases per 100,000 population.⁶

Mortality/Morbidity

Melanoma is second only to adult leukemia in years of potential life lost in young adults. The disease is responsible for death in a disproportionately high number of young and middle-aged adults.

Lentigo maligna melanoma has mortality rate similar to that of other melanoma types if depth of the tumor is taken into account.

About 10% of melanomas are familial. A first-degree relative has an 8-12 times increased risk of melanoma. The major gene resides on chromosome arm 9p and encodes a tumor suppressor gene called CDKN2A or MTS1.⁷ The second gene that has been noted in melanoma prone families is CDK4, and germline mutations have been identified in this group.

Patients with neck and scalp melanoma have shorter survival compared to melanoma at other sites (extremities, face, trunk). In an analysis of the Surveillance, Epidemiology, and End Results (SEER) program data patients with scalp and neck have a 1.84 risk of dying compared to other sites such as extremity melanoma (HR 1.84; confidence interval, 1.62-2.10). The 5- and 10-year Kaplan Meier survival probabilities for scalp and neck melanoma were 83.1% and 76.2%, respectively, compared to melanoma of other sites 92.1% and 88.7%, respectively.

Race

Melanoma is the most frequent cancer in white women aged 25-29 years and the second most frequent (after breast cancer) in white women aged 24-30 years with fair skin.

Sex

A slight female preponderance is seen among patients with lentigo maligna.

Age

Patients with lentigo maligna tend to be older than those with superficial spreading malignant melanoma or nodular melanoma.

• Generally, patients with lentigo maligna are older than 40 years, with a mean age of 65 years.
• The peak incidence occurs in the seventh to eighth decades of life.
• Lentigo maligna and lentigo maligna melanoma are associated with higher occupational exposure and lower recreational sun exposure.

Clinical

History

The risk of lentigo maligna melanoma increases as the number of years of residence in sunnier climates (eg, southern United States) increases, and risk increases with increased hours of exposure to sunlight,⁸ increased amount of actinic damage, and a history of nonmelanoma skin cancer.

• Associations have been reported with the following:
  • Basal cell carcinoma
  • Light skin color (especially people who have red hair)
  • History of severe sunburn
  • Porphyria cutanea tarda
  • Werner syndrome
  • Tyrosine-positive oculocutaneous albinism
  • Xeroderma pigmentosa
• Lentigo maligna most commonly affects the sun-exposed skin of the head and neck, with a predilection for the nose and cheek. In fact, in Australia, the lesions occur more commonly on the right side (driver's side) of the head and neck in men and on the left side (passenger's side) in women. According to the Australian road traffic database, most Australian drivers are men, and most passengers in the front seat are women.
• Suspect the possibility of melanoma if a patient reports a new pigmented lesion or changes in an existing mole. About 50% of melanomas can arise from normal skin with no preexisting lesions.

Physical

Patients with melanoma need a complete and thorough physical examination, especially with focus on skin and lymph nodes. Review of systems should focus on symptoms pertaining to metastatic disease. Melanoma usually metastasizes to lungs, liver, and brain.

The most frequent findings suggesting early melanoma are changes in size or color of a new pigmented lesion or an existing mole. Lentigo maligna most commonly affects the sun-exposed skin of the head and neck, with a predilection for the nose and cheek. Less common sites include the arm, leg, and trunk. The conjunctivae and oral mucosa may become involved when a cutaneous lentigo maligna spreads onto mucosal surfaces. Signs suggestive of a more locally advanced lesion include elevation, burning, itching, pain, or bleeding.

• The simple ABCDE rule of melanoma helps patients as well as physicians to suspect and make an early diagnosis.
  • A - Asymmetry
  • B - Border irregularity
  • C - Color variegation
  • D - Diameter greater than 6 mm (tip of pencil head), although melanoma can occur in lesions less than 6 mm
  • E - Enlargement
• Lentigo maligna, the precursor lesion, has been likened to a stain on the skin. The lesion typically is tan-brown, with differing shades throughout.
• Lentigo maligna can be present for long periods (5-15 y) before invasion occurs, although rapid progression within months has been described. The percentage of lentigo maligna that progress to lentigo maligna melanoma remains unknown, but estimates of the lifetime risk of developing lentigo maligna melanoma in patients diagnosed with lentigo maligna at age 45 years appears to be 5%. The risk for progression to lentigo maligna melanoma appears to be proportional to the size of the lesion of lentigo maligna.⁹
  • Distinguishing lentigo maligna from its invasive counterpart on a clinical basis continues to present diagnostic dilemmas, especially in patients who had prior therapeutic interventions like cryotherapy. It is important to have a low threshold for biopsy of pigmented facial lesions.
  • In one series of 85 excised lesions with a clinical diagnosis of lentigo maligna, more than 50% had invasive lentigo maligna melanoma.
• A strong correlation exists between patients who report finding a nodule and diagnosis of melanoma. Although palpability usually indicates dermal invasion, clinical examination may be unreliable in early invasive lentigo maligna melanoma (lesions <1 mm).
• Assess the total number of all types of moles. More than 50 nevi 2 mm in diameter or larger indicate increased risk.
• Search for dysplastic (clinically atypical) melanocytic nevi. Irregular pigment patterns, such as variegation, central dark areas, or halos of pigment, may indicate the presence of dysplasia. Atypical nevi tend to be larger than common acquired neomelanocytic nevi, which rarely exceed 5 mm.
• Search for congenital melanocytic nevi. People with very large or giant congenital nevi have an increased lifetime risk (>6%) of developing melanoma. Intermediate sized (>0.5 cm), raised, pigmented lesions, with or without hair, that do not have the features of clinically atypical nevi have an uncertain but elevated risk for development of melanoma.

Causes

• Ultraviolet radiation exposure: For people who live in Australia, risk increases as the number of years spent in Australia increases, and risk increases with increased hours of exposure to sunlight, with the amount of actinic damage, and with history of nonmelanoma skin cancer.
• Increased number of melanocytic nevi, including large or giant congenital nevi
• Fair skin
• History of severe sunburn
• Occupational risk

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