Lentigo maligna is where melanocyte cells have become malignant and grow continuously along the stratum basale of the skin, but have not invaded below the epidermis. Lentigo maligna is not the same as lentigo maligna melanoma, as detailed below. It typically progresses very slowly and can remain in a non-invasive form for years. It is normally found in the elderly (peak incidence in the 9th decade), on skin areas with high levels of sun exposure like the face and forearms. Incidence of evolution to lentigo maligna melanoma is low, about 2.2% to 5% in elderly patients. It is also known as "Hutchinsons melanotic freckle". This is named for Jonathan Hutchinson. The word lentiginous comes from the latin for freckle. Relation to melanoma
Lentigo maligna is a histopathological variant of melanoma in situ. Lentigo maligna is sometimes classified as a very early melanoma, and sometimes as a precursor to melanoma.When malignant melanocytes from a lentigo maligna have invaded below the epidermis, the condition is termed lentigo maligna melanoma. Signs and symptoms
Characteristics include a blue/black stain of skin initially. Skin is thin, about 4-5 cell layers thick, which is often related to aging. Histological features include epidermal atrophy and increased number of melanocytes. Diagnosis
First dilemma in diagnosis is recognition. As lentigo malignas often present on severely sun-damaged skin, it is frequently found amongst numerous pigmented lesions – thin seborrheic keratoses, lentigo senilis, lentigines. It is difficult to distinguish these lesions with the naked eye alone, and even with some difficulty using dermatoscopy.
In view of the very poor cure rate with standard excision, some surgeons combine the two methods: surgical excision of the lesion, then three months treatment of the area with imiquimod cream. Studies seem to conflict about the level of certainty associated with using imiquimod.Another treatment to be considered where standard margins cannot be achieved or cosmetics are a major consideration is ultra-soft x-ray/grenz-ray radiation.In the very elderly or those with otherwise limited life expectancy, the impact of major day surgery for excision with 5mm margins and large skin flap could be worse than doing nothing or the possibility of failed treatments with imiquimod or Grenz ray. References
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