Lentigo maligna (also known as " lentiginous melanoma in sun-damaged skin ") is an in situ melanoma consisting of malignant cells but it does not show invasive growth. Malignant lentigo is not the same as lentigo maligna melanoma, and should be discussed separately. It usually lasts very slowly and can remain in non-invasive form for many years. The transition to true melanoma is characterized by the appearance of a wavy surface (itself a marker of vertical growth and invasion), at that point called lentigo maligna melanoma. Usually found in the elderly (peak incidence in the 9th decade), in skin areas with high levels of exposure to sunlight such as the face and forearm. Some authors do not consider lentigo maligna as melanoma. It is generally regarded as a melanoma precursor. The incidence of evolution to lentigo maligna melanoma is very low, around 2.2% to 5% in elderly patients.
It is also known as "Hutchinson's melanotic spots". It's named after Jonathan Hutchinson. The word lentiginous comes from Latin for spots.
Video Lentigo maligna
Presentations
Characteristics include blue/black stains on the skin initially. The skin is thin, about 4-5 layers of thick cells, often associated with aging. Histologic features include epidermal atrophy and increased number of melanocytes.
Maps Lentigo maligna
Diagnosis
The first dilemma in diagnosis is recognition. Because malignant lentigo often appears on very sun-damaged skin, it is often found among many pigmented lesions - thin seborrhoeic keratosis, senile lentigo, lentigine. It is difficult to distinguish this lesion with the naked eye alone, and even with some difficulty using dermatoscopy. Because malignant lentigo is often very large, it often blends with, or includes other skin tumors - such as lentigine, melanocytic naevi, and seborrhoeic keratosis.
The second dilemma is the biopsy technique. Although excisional biopsy (removing whole lesions) is ideal, and is recommended by pathologists; practical reason stated that this should not be done. These tumors are often large and appear in the face area. The excision of such a large tumor would be completely contraindicated if the identity of the lesion is uncertain. The preferred diagnostic method is to use a punch biopsy, which allows the doctor to take samples of multiple pieces of full thickness of the tumor at several sites. While one part of the tumor may exhibit benign melanocytic naevus, another part may indicate features regarding to severe cellular atypia. When cellular atypia is recorded, a pathologist may indicate that all lesions should be removed. It is at this point that one can comfortably remove all lesions, and thus confirm the final diagnosis of malignant lentigo. The size of the biopsy blow may vary from 1 mm to 2 mm, but it is better to use a 1.5 mm or larger punch. Representative samples of atypical parts of most nevus should be biopsied, often guided by dermatoscopy.
Treatment
The best treatment of lentigo maligna is unclear because it has not been well studied.
Standard excision is still performed by most surgeons. Unfortunately, the recurrence rate is high (up to 50%). This is due to a clear operating limit, and the location of the face of the lesion (often forcing the surgeon to use narrow surgical margins). The use of dermatoscopy can significantly improve the ability of surgeons to identify surgical margins. The narrow surgical margin used (smaller than the standard 5 mm treatment), combined with the standard fixed-loop histology technique boundaries - results in a high degree of "negative error" error, and often recurs. Margin control (margin edge) is required to eliminate the wrong negative error. If breadloafing is used, the distance from the portion should be close to 0.1 mm to ensure that the method approaches the complete margin control.
If the lesion is on the face and most likely or a 5mm margin, the skin flap or skin graft can be indicated/required. Crafts have a risk of failure and poor cosmetic outcomes. Flaps can require large incisions that result in long scars and may be better performed by plastic surgeons (and probably better by those with extensive LM experience or "suspicious early melanoma").
Mohs surgery has been performed with a reported cure rate of 77%. The "double scalpel" controlled marginal control method approximates the Mohs method in margin control, but requires a pathologist who is familiar with the complexity of managing vertical margins on thin peripheral parts and staining methods.
Some melanocytic naevi, and melanoma-in-situ (lentigo maligna) have healed with experimental treatment, imiquimod topical cream (Aldara), immune-boosting substances. Given a very poor healing rate with standard excision, some surgeons combine two methods: excision of surgical lesion, then three months of treatment area with imiquimod cream.
The study seems to contradict the degree of certainty associated with the use of imiquimod.
Other treatments to consider if standard margins can not be achieved or cosmetics are a major consideration are ultra-soft x-ray/grenz-ray radiation.
In the elderly or those with limited life expectancy, the impact of day surgery for excision with 5 mm edges and large skin flaps could be worse than not doing anything or possible treatment failure with imiquimod or Grenz rays.
References
External links
- Media related to Lentigo maligna on Wikimedia Commons
Source of the article : Wikipedia
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