Lentigo Maligna

Lentigo maligna is melanoma Melanoma Melanoma is a malignant tumor arising from melanocytes, the melanin-producing cells of the epidermis. These tumors are most common in fair-skinned individuals with a history of excessive sun exposure and sunburns. Melanoma in situ, a precancerous lesion that may progress to an invasive melanoma Melanoma Melanoma is a malignant tumor arising from melanocytes, the melanin-producing cells of the epidermis. These tumors are most common in fair-skinned individuals with a history of excessive sun exposure and sunburns. Melanoma (specifically lentigo maligna melanoma Melanoma Melanoma is a malignant tumor arising from melanocytes, the melanin-producing cells of the epidermis. These tumors are most common in fair-skinned individuals with a history of excessive sun exposure and sunburns. Melanoma subtype). This condition typically occurs in sun-damaged areas (e.g., face and neck) of elderly patients. Lentigo maligna presents as a brown macule with color variegation and asymmetrical borders that grow slowly. The lesion should be biopsied to confirm a diagnosis and surgical excision with a safety margin is the 1st-line treatment.

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Overview

Definition

Lentigo maligna (also known as Hutchinson melanotic freckle) is melanoma Melanoma Melanoma is a malignant tumor arising from melanocytes, the melanin-producing cells of the epidermis. These tumors are most common in fair-skinned individuals with a history of excessive sun exposure and sunburns. Melanoma in situ. This type of precancerous lesion may progress to lentigo maligna melanoma Melanoma Melanoma is a malignant tumor arising from melanocytes, the melanin-producing cells of the epidermis. These tumors are most common in fair-skinned individuals with a history of excessive sun exposure and sunburns. Melanoma.

Epidemiology

  • Peak incidence between 65 and 80 years of age
  • Precursor to the 3rd most common melanoma Melanoma Melanoma is a malignant tumor arising from melanocytes, the melanin-producing cells of the epidermis. These tumors are most common in fair-skinned individuals with a history of excessive sun exposure and sunburns. Melanoma subtype (lentigo maligna melanoma Melanoma Melanoma is a malignant tumor arising from melanocytes, the melanin-producing cells of the epidermis. These tumors are most common in fair-skinned individuals with a history of excessive sun exposure and sunburns. Melanoma)
  • Women > men
  • Incidence is 13.7 per 100,000.

Etiology

  • Genetic mutations:
    • Compared with other melanoma Melanoma Melanoma is a malignant tumor arising from melanocytes, the melanin-producing cells of the epidermis. These tumors are most common in fair-skinned individuals with a history of excessive sun exposure and sunburns. Melanoma subtypes, there is an increased likelihood of KIT mutations.
    • Other mutations include CCND1, MITF, NRAS, and p53.
  • Risk factors:
    • Cumulative (over time) ultraviolet radiation
    • Genetic conditions:
      • Oculocutaneous albinism Oculocutaneous albinism Albinism refers to a group of inherited disorders that result in the disruption of melanin production, causing hypopigmentation and visual impairment. The condition is classified according to the clinical phenotype. Oculocutaneous albinism results in hypopigmentation of the skin, eyes, and hair. Ocular albinism affects only the eyes. Albinism
      • Xeroderma pigmentosum
      • Porphyria cutanea tarda
    • X-ray irradiation
    • Use of estrogen/progesterone 
    • Use of non-permanent hair dye

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Clinical Presentation

  • Majority occur on the head/neck (mainly the cheek).
  • Variable Variable Variables represent information about something that can change. The design of the measurement scales, or of the methods for obtaining information, will determine the data gathered and the characteristics of that data. As a result, a variable can be qualitative or quantitative, and may be further classified into subgroups. Types of Variables color: 
    • Light brown to black (may have color variegation)
    • May have pink/white areas indicating inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation or regression
  • Asymmetric
  • Poorly defined borders
  • Smooth (nonpalpable)
  • Slow growth → speckles (as melanoma Melanoma Melanoma is a malignant tumor arising from melanocytes, the melanin-producing cells of the epidermis. These tumors are most common in fair-skinned individuals with a history of excessive sun exposure and sunburns. Melanoma enlarges)
  • Indicators of possible progression to invasive melanoma Melanoma Melanoma is a malignant tumor arising from melanocytes, the melanin-producing cells of the epidermis. These tumors are most common in fair-skinned individuals with a history of excessive sun exposure and sunburns. Melanoma:
    • Raised/palpable areas
    • Sharp borders
    • Darker pigmentation
  • Surrounding skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin usually manifests solar skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin damage:
    • Actinic keratoses
    • Solar elastosis
    • Solar lentigines
Lentigo maligna

Lentigo maligna: an asymmetric brown macule with color variegation present on the left cheek

Image: “Lentigo maligna” by kilbad. License: CC BY 3.0

Diagnosis

History

  • Amount of sun exposure
  • Other skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin cancers
  • Family history of melanoma Melanoma Melanoma is a malignant tumor arising from melanocytes, the melanin-producing cells of the epidermis. These tumors are most common in fair-skinned individuals with a history of excessive sun exposure and sunburns. Melanoma
  • Hereditary diseases

Physical exam

  • Complete/thorough skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin exam should be performed.
  • Synchronous malignant and premalignant lesions are not uncommon in individuals with extensive sun damage to the skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin.

Dermoscopy

  • Asymmetric pigmented follicular openings (pseudonetwork)
  • Progression of findings:
    • Early stage: peppering of pigmentation around follicular ostia (blue-gray dots)
    • Coalescence of blue-gray dots into polygonal lines and rhomboidal structures
    • Late stage: homogeneous dark-brown to black blotches blocking the follicular ostia

Reflectance confocal microscopy

  • Availability of this technique is limited.
  • Requires specialized training
  • More sensitive, but less specific for lentigo maligna diagnosis than dermoscopy

Histology

  • Gold standard for lentigo maligna diagnosis
  • Sample obtained via:
    • Excisional biopsy (ideal)
    • Punch biopsy/incisional biopsy in cosmetically sensitive sites
    • Deep shave biopsy
  • Findings:
    • Replacement of basal keratinocytes by nests of atypical melanocytes
    • No basement membrane invasion (if present, indicates progression to invasive melanoma Melanoma Melanoma is a malignant tumor arising from melanocytes, the melanin-producing cells of the epidermis. These tumors are most common in fair-skinned individuals with a history of excessive sun exposure and sunburns. Melanoma)
    • Changes of chronic sun damage:
      • Epidermal atrophy
      • Inflammatory dermal infiltrates
      • Effacement of rete ridges
Histopathology of lentigo maligna

Lentigo maligna:
A nest of atypical melanocytes can be noted. The basement membrane is intact. Therefore, this lesion is lentigo maligna (in situ).

Image: “Lentigo maligna” by Sheliza Halani et al. License: CC BY 4.0

Management and Prognosis

Management

Surgical excision:

  • 1st line treatment
  • Procedures:
    • Wide local excision:
      • Margins of 5–10 mm should be obtained.
      • For small lesions with well-delineated borders
    • Staged excisions:
      • Involves histologic examination of the permanent sections
      • Excisions are performed until negative margins are obtained.
      • For large lesions (> 1 cm on the head/neck and > 2 cm on trunk/extremities)
      • For lesions with ill-defined borders 
    • Mohs micrographic surgery:
      • Staged excision that involves examination of frozen sections
      • May not be as reliable as staged excision technique for lentigo maligna

Nonsurgical:

  • Reserved for:
    • Elderly frail patients
    • Patients refusing surgery
    • Large lesions in cosmetically sensitive areas where problematic reconstruction is expected
  • Includes:
    • Radiotherapy
    • Laser
    • Cryosurgery
    • Topical imiquimod

Patient education:

  • Protection from ultraviolet radiation (sunblock, clothing)
  • Self-examination of the skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin

Prognosis

  • Up to 20% of presumed lentigo maligna biopsies are found to have invasive melanoma Melanoma Melanoma is a malignant tumor arising from melanocytes, the melanin-producing cells of the epidermis. These tumors are most common in fair-skinned individuals with a history of excessive sun exposure and sunburns. Melanoma.
  • Can take from < 10 to > 50 years for lentigo maligna to progress to lentigo maligna melanoma Melanoma Melanoma is a malignant tumor arising from melanocytes, the melanin-producing cells of the epidermis. These tumors are most common in fair-skinned individuals with a history of excessive sun exposure and sunburns. Melanoma.
  • 6%–9% recurrence rate after wide excision
  • In the absence of progression to lentigo maligna melanoma Melanoma Melanoma is a malignant tumor arising from melanocytes, the melanin-producing cells of the epidermis. These tumors are most common in fair-skinned individuals with a history of excessive sun exposure and sunburns. Melanoma, lentigo maligna does not shorten life expectancy.
  • No disease-related deaths when complete excision is achieved

Differential Diagnosis

  • Solar lentigo: macular lesions with irregular margins and uniform brown pigmentation on sun-exposed skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin similar to lentigo maligna. Biopsy of these lesions shows no nesting of atypical melanocytes. Solar lentigo is benign and does not require treatment.
  • Melanoma: a skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin malignancy derived from the malignant transformation of melanocytes. The most common type of melanoma Melanoma Melanoma is a malignant tumor arising from melanocytes, the melanin-producing cells of the epidermis. These tumors are most common in fair-skinned individuals with a history of excessive sun exposure and sunburns. Melanoma is superficial spreading melanoma Melanoma Melanoma is a malignant tumor arising from melanocytes, the melanin-producing cells of the epidermis. These tumors are most common in fair-skinned individuals with a history of excessive sun exposure and sunburns. Melanoma, which usually presents as an irregular macule/patch. On histopathologic examination, atypical melanocytes would be detected in the dermis. Lentigo maligna can progress to lentigo maligna melanoma Melanoma Melanoma is a malignant tumor arising from melanocytes, the melanin-producing cells of the epidermis. These tumors are most common in fair-skinned individuals with a history of excessive sun exposure and sunburns. Melanoma. The mainstay of treatment is surgical excision.
  • Atypical nevus Nevus Nevi (singular nevus), also known as "moles," are benign neoplasms of the skin. Nevus is a non-specific medical term because it encompasses both congenital and acquired lesions, hyper- and hypopigmented lesions, and raised or flat lesions. Nevus/Nevi: a benign melanocytic neoplasm that mimics lentigo maligna in appearance as it may be asymmetric and > 6 mm with color variegation. Dermoscopic examination and biopsy are needed to differentiate. Does not require excision if the diagnosis is certain.
  • Seborrheic keratosis Seborrheic keratosis Seborrheic keratosis (SK) is the most common benign epithelial cutaneous neoplasm. The condition consists of immature keratinocytes. Seborrheic keratosis is the most common benign skin tumor in middle-aged and elderly adults and presents as a sharply demarcated, exophytic, skin lesion that may be tan or black and has a "stuck-on" appearance. Seborrheic Keratosis: a benign neoplasm consisting of immature keratinocytes occurring commonly in the elderly. This condition is demarcated, waxy, and has a stuck-on appearance. A biopsy will show abnormal keratinocytes versus melanocytes. Dermoscopy would show cysts and fissures. This neoplasm does not require treatment.
  • Actinic keratosis Actinic keratosis Actinic keratosis (AK) is a precancerous skin lesion that affects sun-exposed areas. The condition presents as small, non-tender macules/papules with a characteristic sandpaper-like texture that can become erythematous scaly plaques. Actinic Keratosis (AK): a precancerous lesion that affects sun-exposed areas (e.g., scalp and hands) in elderly patients. This condition appears as a scaly, slightly elevated lesion that should be excised or treated topically to prevent invasive squamous cell carcinoma Squamous cell carcinoma Cutaneous squamous cell carcinoma (cSCC) is caused by malignant proliferation of atypical keratinocytes. This condition is the 2nd most common skin malignancy and usually affects sun-exposed areas of fair-skinned patients. The cancer presents as a firm, erythematous, keratotic plaque or papule. Squamous Cell Carcinoma development. The only way to differentiate from lentigo maligna is by a biopsy that shows atypical keratinocytes in the basal layer.
  • Dermatofibroma: a common mesenchymal growth of the skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin where skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin fibroblasts are the primary constituents. This condition usually presents as a firm, indurated, mobile nodule measuring about 0.5–1 cm in size. Upon lateral compression, a dimple-like depression is seen in the overlying skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin (“buttonhole” sign). Does not require treatment, but can be surgically excised if bothersome to the patient.

References

  1. Charifa A. (2020). Lentigo Maligna Melanoma. Retrieved February 24, 2021, from https://www.statpearls.com/articlelibrary/viewarticle/24188/
  2. Cohen L.M. (1995). Lentigo maligna and lentigo maligna melanoma Melanoma Melanoma is a malignant tumor arising from melanocytes, the melanin-producing cells of the epidermis. These tumors are most common in fair-skinned individuals with a history of excessive sun exposure and sunburns. Melanoma. J Am Acad Dermatol. 1995 Dec;33(6):923-36; quiz 937-40.
  3. Sober A. J., Olbricht S., Hong A.M. (2019). Lentigo maligna: Clinical manifestations, diagnosis, and management. Retrieved February 24, 2021, from https://www.uptodate.com/contents/lentigo-maligna-clinical-manifestations-diagnosis-and-management

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