Lentigo maligna


Also known as Hutchinson melanotic freckle.

The most common form of melanoma in situ.

Presents as a slow-growing, variably pigmented macule or patch on chronically sun exposed skin of elderly patients.

It is most common the head & neck region.

The incidene in the adult population estimated to be approximately 13.7 100000 person – years.

Mainly occurs in fair-skinned elderly individuals, with a peak incidence between 7th and 8th decade of life.

Slight female predominance, presumably because women live longer than men.

UV exposure has an important etiologic role, since lesions are more common in sun exposed areas, and in patients with a history of sunburns.

Other risk factors include the history of non-melanoma skin cancers and tendency to form solar lentigines.

Can develop de novo or within an existing solar lentigo.

Patients have a higher incidence of two more protein p53 gene mutations.

Microscopically manifest as a proliferation of atypical melanocytes at the basal level of the epidermis and within the hair follicles, nesting of atypical melanocytes, and effacement of rete ridges.

No dermal invasion is present.

Chronic sun damage changes including epidermal atrophy and elastic tissue degeneration within the dermis is usually present.

Manifest as a solitary, very slow growing, asymmetric, macule or patch, ill-defined or irregular borders, and variegated colors ranging from tan-brown to dark black.

Surface is flat and usually smooth.

Black pigmentation is also found.

Predilection for sun exposed areas such as head and neck, with a predilection for the cheek.

Approximately 86% cases occur in the head and neck area.

May be seen in the upper back, forearms, and legs.

Diagnosis is made on suspicious clinical findings.

Diagnosis is aided with the use of dermoscopy and less commonly reflectance confocal microscopy.

Thermoscopic findings include asymmetric perifollicular pigmentation, homo genius areas with obliteration of follicular openings, increased vascularity, red or dark rhomboidal structures, annular granular pattern, gray dots and slate gray globules.

Standard for diagnosis includes tissue biopsy, and is considered if the diagnosis is in doubt or when dermascope examination discloses a gray color.

Differential diagnosis includes lentigo maligna melanoma which is a subset of melanoma rising in chronically sun expose skin, seen most commonly in elderly white individuals.

In lentigo maligna melanoma atypical melanocytes are not confined to the epidermis, but are arranged along the epidermal – dermal Junction.

In lentigo maligna melanoma the lesion is darker and more variegated in color, has sharp of borders, and has elevated areas compared with that of lentigo maligna.

Lentigo maligna can undergo malignant transformation to lentigo maligna melanoma, and can manifest as increasingly dark pigmentation, color variegation, development of an elevated area, increase in size, and increased border irregularity.

Lifetime risk of progression to lentigo maligna melanoma ranges from 5 to 20%.

Lentigo maligna has significant risk for recurrence even after adequate treatment.

The use of sunscreens and protective attire is essential for prevention.

Treatment of choice is surgical resection.

Surgical excision to include wide safety margin of greater than 5 mm is advocated, with a staged excision with Mohs surgery is typical.

Mohs surgery has a 5-year recurrence rate of approximately 1.9%, whereas wide surgical excision has a 5-year recurrence rate of less than 5.9%.

When surgery is not an option radiation therapy, laser therapy, and topical and imiquimod with without topical Tarazotene are options.

Laser therapy is associated with a high recurrence rate.

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