Acral melanoma is something which worries every podiatrist – a rare malignancy but one not to be missed as timely diagnosis can reduce morbidity and mortality. Pigmented lesions on the plantar surface always warrant careful examination to rule out melanoma. The traditional ABCDE acronym [1] can be helpful but is not always reliable particularly on the plantar surface and with some nodular melanoma. The CUBED acronym [2] overcomes this with an approach based on specific clinical features. Most recently we have seen the rise of dermoscopy as a technique in the evaluation of pigmented lesions – with a recent study highlighting how podiatrists can improve their clinical skills at recognising melanoma arising on the foot by adopting dermoscopy [3].
Acral Melanoma arising on the sole
Acral melanoma, a term generally denoting melanoma which arises on the palms and the soles, accounts for around 70% of all melanoma arising in African Americans and around 50% in Asian populations. In white populations, this drops to less than 10% as the proportion is lower with more melanoma arising elsewhere on the skin. However, the absolute numbers of acral melanoma occurring are equal in all skin types. Studies consistently report that melanoma on the soles is associated with a poorer prognosis than lesions elsewhere [4-6]. Although few studies have shown plantar melanoma to be a more aggressive tumour, it most likely due to late presentation owing to its remote location or due to diagnostic delays [7, 8] .
For those familiar with the technique, dermoscopy for evaluating pigmented lesions on the palms and plantar surface relies on a technique identifying the location of the pigmentation. Pigmentation in the ridges being indicative of melanoma and pigmentation in the furrows is associated with benign naevi. However, as the science and research into dermoscopy continues, adjustments and improvements continue to be made in analysis of lesions. Whilst this method has been shown to be clinically useful, it has been noted that up to a third of plantar melanoma do not show a parallel ridge pattern, meaning that some malignant lesions may go undetected.
In attempt to accommodate this issue, a group of international researchers explored and developed a new acronym to help improve detection of melanoma, without the parallel ridge pattern [9]. By examining a set of over 600 dermatoscopic images of plantar lesions, assessors were asked to describe the key features in each but did not know whether they were benign or malignant. Consequently, their data was analysed and compared with other assessors, when the diagnosis was revealed to correlate features common to acral melanoma. From this the BRAAF checklist was constructed:
The system is straightforward and easy to use. Essentially the criteria are applied to the lesion in question and a score is generated. Any score equal to or greater than 1 warrants a referral for excision. The checklist was consequently re-tested against the images and found to correctly identify the diagnosis 88.1% of the time. The checklist was found to have a sensitivity of 93.1% (meaning 93.1% of patients with melanoma were correctly identified) and a specificity of 86.7% (the number of benign lesions which were correctly identified as benign using the checklist).
References
1. Friedman, R.J., D.S. Rigel, and A.W. Kopf, Early detection of malignant melanoma: the role of physician examination and self-examination of the skin. CA Cancer J Clin, 1985. 35(3): p. 130-51.
2. Bristow, I.R., et al., Clinical guidelines for the recognition of melanoma of the foot and nail unit. J Foot Ankle Res, 2010. 3(25).
3. Serra-Garcia, L., et al., Dermoscopy training course improves podiatrists' accuracy in diagnosing lesions suggestive of acral melanoma: A cross-sectional study. Australas J Dermatol, 2021.
4. Bradford, P.T., et al., Acral Lentiginous Melanoma: Incidence and Survival Patterns in the United States, 1986-2005. Arch Dermatol, 2009. 145(4): p. 427-434.
5. Hsueh, E., et al., Survival of patients with melanoma of the lower extremity decreases with distance from the trunk. Cancer Causes and Control, 1998. 85: p. 383-388.
6. Talley, L.I., et al., Clinical Outcomes of Localized Melanoma of the Foot: A Case-Control Study. Journal of Clinical Epidemiology, 1998. 51(10): p. 853-857.
7. Metzger, S., et al., Extent and consequences of physician delay in the diagnosis of acral melanoma. Melanoma Res, 1998. 8(2): p. 181-6.
8. Blum, A., et al., Awareness and early detection of cutaneous melanoma: an analysis of factors related to delay in treatment. Br J Dermatol, 1999. 141(5): p. 783-7.
9. Lallas, A., et al., The BRAAFF checklist: a new dermoscopic algorithm for diagnosing acral melanoma. British Journal of Dermatology, 2015. 173(4): p. 1041-1049.