Clinical and pathological features of acral melanoma in a South African population: A retrospective study

Acral melanoma (AM) is a rare subtype of cutaneous melanoma (CM) that disproportionately affects skin of colour and carries a poorer prognosis than other melanoma subtypes. The poor prognosis is attributed to late diagnosis and subsequent relatively high Breslow thickness, but also to an intrinsic biological aggressiveness. Scientific data on AM from the developing world are limited and a need exists to characterise the disease further in the South African (SA) population.

To describe the clinical and pathological features of AM in an SA population.

A retrospective chart review characterised the demographics, clinical features and histological data of 66 patients diagnosed with AM between January 2010 and June 2016 at Tygerberg Academic Hospital, Cape Town, SA.

Sixty-six patients with AM were identified from 335 patients diagnosed with CM during the set time frame. The mean age (standard deviation (SD)) was 61.5 (12.5) years. Forty-two (63.6%) of the patients were female (male/female ratio 1:1.75). The majority of patients diagnosed with AM were black (48.5%), and the proportion of AM in black patients with CM was 80.0%. Fifty-six AMs (84.8%) were located on the foot and 10 (15.2%) on the hand. The median duration of the lesion before diagnosis was 10 months (range 2 - 84) and the mean (SD) tumour size was 3.8 (2.2) cm at diagnosis. The mean Breslow thickness of all AMs at diagnosis was 5.2 mm (median 4.2  mm, range 0 - 22). Stage of disease was known in 41 patients, 23 (56.1%) of whom had at least stage III disease at diagnosis. Mean Breslow thickness for foot and hand melanomas was 4.9 mm (range 0 - 22) and 6.9 mm (range 0 - 13.3), respectively (p=0.2552). The mean Breslow thickness in the black population was 6.3 mm compared with 4.2 mm and 4.3 mm, respectively, in the white and coloured populations (p=0.178). Patients from outside the Western Cape Province (WC) presented with a mean Breslow thickness of 6.6 mm (range 0 - 14.5) and patients from the WC with a mean Breslow thickness of 4.9 mm (range 0 - 22) (p=0.3602).

AMs accounted for a significant proportion of all CMs diagnosed. Patients presented with an advanced stage of disease at diagnosis, and further studies are needed to further investigate the reasons for delayed diagnosis.