Lentigo maligna is a form of melanoma in situ, meaning it is a very early stage of skin cancer. It primarily affects skin areas with significant sun exposure. While serious, its potential to become life-threatening largely depends on whether it progresses beyond its initial, non-invasive stage.
Understanding Lentigo Maligna
Lentigo maligna (LM) is a type of melanoma where cancer cells are confined to the outermost layer of the skin, the epidermis, meaning they have not yet penetrated deeper skin layers. LM typically appears as a flat, discolored patch, often light brown or tan, which can slowly enlarge and develop irregular borders.
These lesions are most commonly found on chronically sun-damaged skin, particularly on the face, neck, and scalp, but can also appear on the arms and back. The primary cause of lentigo maligna is long-term, cumulative exposure to ultraviolet (UV) radiation from the sun.
Progression to Invasive Melanoma
Lentigo maligna has the potential to progress into an invasive form called lentigo maligna melanoma (LMM). This occurs when malignant cells break through the epidermis and invade the dermis. Once in the dermis, these cancer cells can spread to other body parts, such as lymph nodes or distant organs, through the lymphatic system or bloodstream. This spread, known as metastasis, makes LMM potentially fatal if not detected and treated early.
The transition from LM to LMM is typically slow, often over many years. Signs of progression include changes in the lesion’s appearance, such as increased thickness, elevation, or the development of a nodule. Other concerning signs include color changes to darker shades like black or blue, or symptoms like bleeding, itching, or stinging within the patch.
Diagnosis and Treatment
Identifying lentigo maligna early is important for preventing its progression to an invasive melanoma. The diagnostic process typically begins with a thorough clinical examination of suspicious skin lesions. Doctors often use a dermatoscope, a handheld device with magnification and light, to closely examine the characteristics of the lesion. If LM is suspected, a skin biopsy is performed to confirm the diagnosis, allowing a pathologist to examine the cells under a microscope.
Surgical excision is the standard and often preferred treatment for lentigo maligna, aiming to completely remove the lesion and a margin of healthy surrounding skin. Mohs micrographic surgery is frequently used for LM, especially on the face and neck, due to its precision in removing cancerous cells while preserving healthy tissue. This technique involves removing thin layers of skin and examining them under a microscope immediately until all cancer cells are gone. Other treatment options, particularly for cases where surgery is challenging, include topical therapies like imiquimod cream, which stimulates an immune response, and radiation therapy.
Prognosis and Long-Term Outlook
When lentigo maligna is diagnosed and treated early, the prognosis is generally favorable, with a very high cure rate. Effective treatment typically prevents the disease from becoming life-threatening. The risk of recurrence after surgical removal can be up to 20%, highlighting the need for thorough initial treatment.
If lentigo maligna progresses to invasive lentigo maligna melanoma (LMM), the prognosis becomes more serious, similar to other invasive melanomas. For localized LMM that has not spread, the five-year survival rate can be 100%. However, if LMM spreads to nearby lymph nodes or distant parts of the body, survival rates decrease. Regular follow-up appointments with a dermatologist and consistent self-skin exams are important for individuals who have had LM or LMM to monitor for new lesions or signs of recurrence.