Which physical findings are characteristic of lentigo maligna melanoma?

Updated: Dec 19, 2019
  • Author: Winston W Tan, MD, FACP; Chief Editor: William D James, MD  more...
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Patients with melanoma need a complete and thorough physical examination, especially with focus on the skin and lymph nodes.

The most frequent findings that suggest 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. 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.

Less common sites of involvement 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, as follows, 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

Clinical characteristics of lentigo maligna include the following:

  • Large size: > 6 mm and often several centimeters in diameter at diagnosis
  • Irregular shape
  • Variable pigmentation: Colors may include light brown or tan, dark brown, pink, red, or white
  • Smooth surface

Lentigo maligna, the precursor lesion, has been likened to a stain on the skin. The lesion is typically tan-brown, with differing shades throughout.

Assess the total number of all types of moles. More than 50 nevi 2 mm in diameter or larger indicate an increased risk for melanoma.

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.

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