Acral lentiginous melanoma

Synonyms

3

Overview

Acral lentiginous melanoma is observed on the palms, soles and under the nails. It occurs on non hair-bearing surfaces of the body which may or may not be exposed to sunlight. It is also found on mucous membranes. Unlike other forms of melanoma, acral lentiginous melanoma does not appear to be linked to sun exposure.

Symptoms

• Longitudinal tan, black, or brown streak on a finger or toe nail (melanonychia striata)
• Pigmentation of proximal nail fold
• Areas of dark pigmentation on palms of hands or soles of feet
• Dark pigmented area on soles
• Dark pigmented area on palms
• Dark streaks along fingernail
• Dark streaks along toenail
• Darkened base of nail

Causes

The cause or causes of acral lentiginous melanoma are unknown. It is not related to sun exposure.

Acral lentiginous melanoma is relatively rare compared to other types of melanoma. There is no connection with the colour of skin (skin phototype) and it occurs at equal rates in white, brown or black skin. Acral lentiginous melanoma accounts for 29-72% of melanoma in dark-skinned individuals but less than 1% of melanoma in fair skinned people, as they are prone to more common sun-induced types of melanoma such as superficial spreading melanoma and lentigo maligna melanoma. Acral lentiginous melanoma is equally common in males and females. The majority arise in people over the age of 40.

Diagnosis

Initial confirmation of the suspicion can be done with a small wedge biopsy or small punch biopsy. Thin deep wedge biopsies can heal very well on acral skin, and small punch biopsies can give enough clue to the malignant nature of the lesion. Once this confirmatory biopsy is done, a second complete excisional skin biopsy can be performed with a narrow surgical margin (1 mm).

Prognosis

The prognosis of Acral lentiginous melanoma usually refers to the likely outcome of Acral lentiginous melanoma. The prognosis of Acral lentiginous melanoma may include the duration of Acral lentiginous melanoma, chances of complications of Acral lentiginous melanoma, probable outcomes, prospects for recovery, recovery period for Acral lentiginous melanoma, survival rates, death rates, and other outcome possibilities in the overall prognosis of Acral lentiginous melanoma.

Treatment

The initial treatment of a primary melanoma is to cut it out; the lesion should be completely excised with a 2-3 mm margin of normal tissue. Further treatment depends mainly on the Breslow thickness of the lesion.

After initial excision biopsy; the radial excision margins, measured clinically from the edge of the melanoma, recommended in the The Australian and New Zealand Guidelines for the Management of Melanoma (2008) are shown in the table below. This may necessitate flap or graft to close the wound. In the case of acral lentiginous and subungual melanoma, this may include partial amputation of a digit. Occasionally, the pathologist will report incomplete excision of the melanoma, despite wide margins. This means further surgery or radiotherapy will be recommended to ensure the tumour has been completely removed.

Resources

• NIH
• DermNet NZ