Lentigo Maligna and Lentigo Maligna Melanoma

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In a previous post we defined the skin cancer term, melanoma in situ, as the earliest and most treatable stage of melanoma. Lentigo maligna (LM) is a subtype of melanoma in-situ. If this cancer progresses it is diagnosed as Lentigo Maligna Melanoma (LMM). We will discuss this type of melanoma skin cancer and the latest research findings on risk factors associated with developing this variation of melanoma.

Lentigo Maligna (LM)

Lentigo Maligna is a term used to describe the beginning stages of lentigo maligna melanoma where the cancer cells are confined to the epidermal skin layer. It may look like a brown flat patch which may spread and grow slowly over a period of years. The lesion may have irregular borders and have various shades of tan to brown. It usually develops on the face in areas of long term sun exposure. It can easily be mistaken in this early stage for what people commonly refer to as age spots or sun spots.

Lentigo Maligna Melanoma (LMM)

If the lesion is invasive and grows into the dermis, it is then called lentigo maligna melanoma. The period of years before lentigo maligna becomes an invasive melanoma can be as long as 5-15 years. The Cleveland Clinic Center for Continuing Education reports that less than 30%-50% of the lentigo maligna lesions will progress to becoming invasive lentigo maligna melanomas. Some sources say that the risk of progression to advanced stages may be proportional to the size of the pre-malignant lesion.

At this stage the borders and coloring of the lesion may grow more irregular. There may be various shades of tan, brown and black. As the cancer grows dark bumps may appear and if they are large enough, can feel lumpy to the touch. Signs of an advanced lesion can include burning, itching, pain, or bleeding.

Lentigo maligna melanoma primarily develops on the head, neck, nose and cheeks where the skin has had long term exposure to the sun. The median age at diagnosis is 65 years. It is more common among the elderly, especially those who are in their 70's and 80's.

If you wish to see what this type of melanoma looks like, The New Zealand Dermatological Society has many images on their website of lentigo maligna melanoma skin cancers.

The Latest Research on Lentigo Maligna Melanoma

In a recent study published in Dermatology Times, Dr. Eleni Linos and colleagues took a look at the impact of lifetime UV exposure on LMM. Here are some of the highlights of this study:

  • The study authors concluded that chronic ultraviolet (UV) light exposure raises the risk of lentigo maligna melanoma (LMM).

  • Previous researchers have shown that patients with LMM have many more solar keratoses, a marker of chronic actinic damage, compared to patients with melanomas on the trunk.

  • The mean age of patients with LMM was 66 years, slightly older than for other melanomas.

  • Associations appear strongest among those who stayed in an area of high UV residence from birth throughout adulthood.

It is logical to assume that prevention consists of developing sun safety habits. For more information about how to prevent melanoma or other skin cancers please read the following articles provided by Skin Cancer Connection: