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A 65-year-old woman noted that a brown spot on her face was growing larger and darker (Figure 168-1). A broad shave biopsy showed lentigo maligna (LM) (melanoma in situ). The patient was referred for Mohs surgery for definitive treatment.

Figure 168-1

Lentigo maligna (melanoma in situ) on the face. (With permission from Usatine RP, Moy RL, Tobinick EL, Siegel DM. Skin Surgery: A Practical Guide. St. Louis, MO: Mosby; 1998.)

LM begins as a tan-brown macule melanoma usually in sun-damaged areas of the skin in older individuals. It is a subtype of melanoma in situ.

Hutchinson melanotic freckle.

  • The incidence of LM is directly related to sun exposure. In the United States, the incidence is greatest in Hawaii, intermediate in the central and southern states, and lowest in the northern states.1
  • Generally, patients with LM are older than age 40 years, with a peak incidence between the ages of 65 and 80 years.2
  • Persons with LM melanoma (LMM) tend to be older, fair-skinned persons with markers of actinic skin damage and prior skin cancers, and the incidence is increasing.3
  • The lesions occur more commonly on the driver's side of the head and neck in men in Australia.4

  • LM is a subtype of melanoma in situ, a preinvasive lesion confined to the epidermis (Figures 168-1, 168-2, and 168-3).
  • It is caused by cumulative sun exposure and, therefore, seen later in life.
  • LMM occurs when the lesion extends into the dermis (Figure 168-4).
  • LM can be present for long periods (5 to 15 years) before invasion occurs, although rapid progression within months has been described.5
  • The risk for progression to LMM appears to be proportional to the size of the lesion of LM.5

Figure 168-2

LM on the face, presenting as a single large evolving pigmented lesion with changing color. (With permission from Usatine RP, Moy RL, Tobinick EL, Siegel DM. Skin Surgery: A Practical Guide. 1998, St. Louis: Mosby.)

Figure 168-3

LM on the ear (melanoma in situ). (With permission from Usatine RP, Moy RL, Tobinick EL, Siegel DM. Skin Surgery: A Practical Guide. St. Louis, MO: Mosby; 1998.)

Figure 168-4

LMM on the cheek. This lesion is invasive and no longer melanoma in situ. A partial broad scoop shave biopsy is a good way to make this diagnosis, as a full depth complete excisional biopsy would be prohibitively large and a punch biopsy might miss the diagnosis. (Courtesy of the Skin Cancer Foundation. For ...

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