Lentigo maligna
Encyclopedia
Lentigo
maligna (also known as "Lentiginous melanoma on sun-damaged skin") is a melanoma
in situ
that consists of malignant
cells but does not show invasive growth. Lentigo maligna is not the same as lentigo maligna melanoma
, and should be discussed separately. It typically progresses very slowly and can remain in a non-invasive form for years. The transition to true melanoma is marked by the appearance of a bumpy surface (itself a marker of vertical growth and invasion), at which point it is called lentigo maligna melanoma
. 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. Some authors do not consider lentigo maligna to be a melanoma. It is commonly thought of as a melanoma precursor. Incidence of evolution to lentigo maligna melanoma is very low, about 2.2% to 5% in elderly patients.
It is also known as "Hutchinson's melanotic freckle". This is named for Jonathan Hutchinson
.
s.
. As the lentigo maligna is often very large, it often merges with, or encompasses other skin tumors - such as lentigines, melanocytic nevi, and seborrheic keratosis.
Second dilemma is the biopsy technique. Even though excisional biopsy (removing the entire lesion) is ideal, and advocated by pathologists; practical reason dictates that this should not be done. These tumors are often large and presenting on the facial area. Excision of such large tumor would be absolutely contraindicated if the lesion's identity is uncertain. The preferred method of diagnosis is by using a punch biopsy, allowing the physician to sample multiple full thickness pieces of the tumor at multiple sites. While one section of the tumor might show benign melanocytic nevus, another section might show features concerning of severe cellular atypia. When cellular atypia is noted, a pathologist might indicate that the entire lesion should be removed. It is at this point that one can comfortable remove the entire lesion, and thus confirming the final diagnosis of lentigo maligna. The size of the punch biopsy can vary from 1 mm to 2 mm, but it is preferred to use a punch 1.5 mm or larger. Representative samples of the most atypical parts of the nevus should be biopsied, often guided by dermatoscopy
.
can significantly improve the surgeon's ability to identify the surgical margin. The narrow surgical margin used (smaller than the standard of care of 5 mm), combined with the limitation of the standard bread loafing technique of fixed tissue histology - result in a high "false negative" error rate, and frequent recurrences. Margin controlled (peripheral margins) is necessary to eliminate the false negative errors. If breadloafing is utilized, distances from sections should approach 0.1 mm to assure that the method approaches complete margin control.
Where the lesion is on the face and either large or 5mm margins are possible, a skin flap or skin graft may be indicated/required. Grafts have their own risks of failure and poor cosmetic outcomes. Flaps can require extensive incision resulting in long scars and may be better done by plastic surgeons (and possibly better again by those with extensive LM or "suspicious of early malignant melanoma" experience.
Mohs surgery
has been done with cure rate reported to be 77%. The "double scalpel" peripheral margin controlled excision method approximates the Mohs method in margin control, but requires a pathologist intimately familiar with the complexity of managing the vertical margin on the thin peripheral sections and staining methods.
Some melanocytic nevi, and melanoma-in-situ (lentigo maligna) have resolved with an experimental treatment, imiquimod
(Aldara) topical cream, an immune enhancing agent. 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. Compare studies by Lena Li et al and A. M. Powell et al
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 the outcome of watchful waiting or the possibiity of failed treatments with Imiquimod or Grenz ray.
Some cities have specialist melanoma institutes such as the Melanoma Institute of Australia's Poche Centre in North Sydney, Australia.
Lentigo
A lentigo is a small pigmented spot on the skin with a clearly-defined edge, surrounded by normal-appearing skin. It is a harmless hyperplasia of melanocytes which is linear in its spread. This means the hyperplasia of melanocytes is restricted to the cell layer directly above the basement...
maligna (also known as "Lentiginous melanoma on sun-damaged skin") is a melanoma
Melanoma
Melanoma is a malignant tumor of melanocytes. Melanocytes are cells that produce the dark pigment, melanin, which is responsible for the color of skin. They predominantly occur in skin, but are also found in other parts of the body, including the bowel and the eye...
in situ
In situ
In situ is a Latin phrase which translated literally as 'In position'. It is used in many different contexts.-Aerospace:In the aerospace industry, equipment on board aircraft must be tested in situ, or in place, to confirm everything functions properly as a system. Individually, each piece may...
that consists of malignant
Malignant
Malignancy is the tendency of a medical condition, especially tumors, to become progressively worse and to potentially result in death. Malignancy in cancers is characterized by anaplasia, invasiveness, and metastasis...
cells but does not show invasive growth. Lentigo maligna is not the same as lentigo maligna melanoma
Lentigo maligna melanoma
Lentigo maligna melanoma is a melanoma that has evolved from a lentigo maligna. They are usually found on chronically sun damaged skin such as the face and the forearms of the elderly. The nomenclature is very confusing to both patients and physicians alike....
, and should be discussed separately. It typically progresses very slowly and can remain in a non-invasive form for years. The transition to true melanoma is marked by the appearance of a bumpy surface (itself a marker of vertical growth and invasion), at which point it is called lentigo maligna melanoma
Lentigo maligna melanoma
Lentigo maligna melanoma is a melanoma that has evolved from a lentigo maligna. They are usually found on chronically sun damaged skin such as the face and the forearms of the elderly. The nomenclature is very confusing to both patients and physicians alike....
. 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. Some authors do not consider lentigo maligna to be a melanoma. It is commonly thought of as a melanoma precursor. Incidence of evolution to lentigo maligna melanoma is very low, about 2.2% to 5% in elderly patients.
It is also known as "Hutchinson's melanotic freckle". This is named for Jonathan Hutchinson
Jonathan Hutchinson
Sir Jonathan Hutchinson , was an English surgeon, ophthalmologist, dermatologist, venereologist and pathologist.-Life:He was born in Selby, Yorkshire, England of Quaker parents and educated in the local school...
.
Presentation
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 melanocyteMelanocyte
-External links: - "Eye: fovea, RPE" - "Integument: pigmented skin"...
s.
Pathology Images
See Wikimedia Commons for Lentigo Maligna imagesDiagnosis
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 dermatoscopyDermatoscopy
Dermatoscopy is the examination of skin lesions with a dermatoscope...
. As the lentigo maligna is often very large, it often merges with, or encompasses other skin tumors - such as lentigines, melanocytic nevi, and seborrheic keratosis.
Second dilemma is the biopsy technique. Even though excisional biopsy (removing the entire lesion) is ideal, and advocated by pathologists; practical reason dictates that this should not be done. These tumors are often large and presenting on the facial area. Excision of such large tumor would be absolutely contraindicated if the lesion's identity is uncertain. The preferred method of diagnosis is by using a punch biopsy, allowing the physician to sample multiple full thickness pieces of the tumor at multiple sites. While one section of the tumor might show benign melanocytic nevus, another section might show features concerning of severe cellular atypia. When cellular atypia is noted, a pathologist might indicate that the entire lesion should be removed. It is at this point that one can comfortable remove the entire lesion, and thus confirming the final diagnosis of lentigo maligna. The size of the punch biopsy can vary from 1 mm to 2 mm, but it is preferred to use a punch 1.5 mm or larger. Representative samples of the most atypical parts of the nevus should be biopsied, often guided by dermatoscopy
Dermatoscopy
Dermatoscopy is the examination of skin lesions with a dermatoscope...
.
Treatment
Standard excision is still being done by most surgeons. Unfortunately, the recurrence rate is exceedingly high (up to 50%). This is due to the ill defined visible surgical margin, and the facial location of the lesions (often forcing the surgeon to use a narrow surgical margin). The use of dermatoscopyDermatoscopy
Dermatoscopy is the examination of skin lesions with a dermatoscope...
can significantly improve the surgeon's ability to identify the surgical margin. The narrow surgical margin used (smaller than the standard of care of 5 mm), combined with the limitation of the standard bread loafing technique of fixed tissue histology - result in a high "false negative" error rate, and frequent recurrences. Margin controlled (peripheral margins) is necessary to eliminate the false negative errors. If breadloafing is utilized, distances from sections should approach 0.1 mm to assure that the method approaches complete margin control.
Where the lesion is on the face and either large or 5mm margins are possible, a skin flap or skin graft may be indicated/required. Grafts have their own risks of failure and poor cosmetic outcomes. Flaps can require extensive incision resulting in long scars and may be better done by plastic surgeons (and possibly better again by those with extensive LM or "suspicious of early malignant melanoma" experience.
Mohs surgery
Mohs surgery
Mohs surgery, also known as chemosurgery, created by a general surgeon, Dr. Frederic E. Mohs, is microscopically controlled surgery used to treat common types of skin cancer. It is one of the many methods of obtaining complete margin control during removal of a skin cancer using frozen section...
has been done with cure rate reported to be 77%. The "double scalpel" peripheral margin controlled excision method approximates the Mohs method in margin control, but requires a pathologist intimately familiar with the complexity of managing the vertical margin on the thin peripheral sections and staining methods.
Some melanocytic nevi, and melanoma-in-situ (lentigo maligna) have resolved with an experimental treatment, imiquimod
Imiquimod
Imiquimod is a prescription medication that acts as an immune response modifier. It is marketed by Meda AB, Graceway Pharmaceuticals and iNova Pharmaceuticals under the trade names Aldara and Zyclara, and by Mochida as Beselna. It is also referred to as R-837.- History :The original FDA approval...
(Aldara) topical cream, an immune enhancing agent. 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
Imiquimod
Imiquimod is a prescription medication that acts as an immune response modifier. It is marketed by Meda AB, Graceway Pharmaceuticals and iNova Pharmaceuticals under the trade names Aldara and Zyclara, and by Mochida as Beselna. It is also referred to as R-837.- History :The original FDA approval...
cream.
Studies seem to conflict about the level of certainty associated with using Imiquimod. Compare studies by Lena Li et al and A. M. Powell et al
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 the outcome of watchful waiting or the possibiity of failed treatments with Imiquimod or Grenz ray.
Some cities have specialist melanoma institutes such as the Melanoma Institute of Australia's Poche Centre in North Sydney, Australia.