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.
Lentigo simplex  is the most common form of lentigo. : 29  A single lesion or multiple lesions (lentigines) may be present at birth or more commonly first develop in early childhood. Lentigo simplex is not induced by sun exposure, and it is not associated with any medical diseases or conditions. It is also referred to as simple lentigo and juvenile lentigo. This condition also affects cats, those with orange coloration most often, and can appear on the nose, lips, and eyes as the cat ages. See also
Balloon cell nevus
List of cutaneous conditions

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