Acral melanoma is a subtype of cutaneous melanoma, which manifests on the palms, wrists and soles of the feet (including the nail unit). Melanoma on the soles of the feet may be unnoticed by the patient for many years, and can be misdiagnosed as other podiatric skin conditions, including plantar warts.
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Acral melanoma is a subtype of cutaneous melanoma, which manifests on the palms, wrists and soles of the feet (including
the nail unit). Melanoma on the soles of the feet may be unnoticed by the patient for many years, and can be misdiagnosed
as other podiatric skin conditions, including plantar warts.1
The annual incidence of melanoma in New Zealand is approximately 35 to 40 cases per 100,000 people; acral melanomas
constitute a minority of these cases (< 5%).2, 3 In people of European descent, 95% of melanomas are due to exposure
to ultraviolet radiation, which is not thought to be an important factor for the development of acral melanomas.4 However,
acral melanomas make up a larger proportion of all melanomas in darker-skinned populations (including Pacific peoples),5
and a substantial number of these occur on the feet.
Acral melanomas are typically thicker than other forms of melanoma at diagnosis and patients have a poorer prognosis,
likely due to a later stage at presentation and diagnosis.6 Acral melanoma can be found on any area of the foot, including
weight bearing sites and the sides of the foot.7 Lesions usually have a persistent irregular stain, with asymmetry of
colour and structure.8 Diagnosis of acral melanoma can be difficult if patients have hyperkeratotic lesions, with little
or no pigmentation, similar to plantar warts (amelanotic or hypomelanotic melanoma – Figure 1).1, 8 A parallel-ridge pattern
of pigmentation seen on dermatoscopy is suggestive of acral melanoma.8 Blue colouration is indicative of invasive melanoma.
Acral melanoma may also involve the nail apparatus where it may present as atypical longitudinal melanonychia (a slowly
widening and irregular band of discolouration in the nail plate), nail destruction or an irregular patch or nodule (which
may be non-pigmented) in the skin lateral to, distal to, or under the nail plate.
Patients with suspected acral melanoma should be referred to a dermatologist to confirm the diagnosis.
References
- Guarneri C, Valenti G. More than a plantar wart. J Hosp Med Off Publ Soc Hosp Med 2010;5:E28.
- Richardson A, Fletcher L, Sneyd M, et al. The incidence and thickness of cutaneous malignant melanoma in New Zealand
1994-2004. N Z Med J 2008;121:18–26.
- Martin RCW, Robinson E. Cutaneous melanoma in Caucasian New Zealanders: 1995−1999. ANZ J Surg 2004;74:233–7.
- Bradford PT, Goldstein AM, McMaster ML, et al. Acral lentiginous melanoma: incidence and survival patterns in the
United States, 1986-2005. Arch Dermatol 2009;145:427–34.
- Stubblefield J, Kelly B. Melanoma in non-caucasian populations. Surg Clin N Am 2014;94:1115-26.
- Durbec F, Martin L, Derancourt C, et al. Melanoma of the hand and foot: epidemiological, prognostic and genetic
features. A systematic review. Br J Dermatol 2012;166:727–39.
- Jung HJ, Kweon S-S, Lee J-B, et al. A clinicopathologic analysis of 177 acral melanomas in Koreans: relevance of
spreading pattern and physical stress. JAMA Dermatol 2013;149:1281–8.
- Dalmau J, Abellaneda C, Puig S, et al. Acral melanoma simulating warts: dermoscopic clues to prevent missing a
melanoma. Dermatol Surg 2006;32:1072–8.