See Pink? Stop and Think!
Malignant melanoma continues to be a problem with increasing incidence in the developed world. Lesions on the feet, particularly on the soles, are most frequently a sub-type classified as acral lentiginous melanoma (ALM). In 2010, we undertook a project to increase awareness of foot melanoma and how it may present on the foot as our earlier work reported that mis-diagnosis and subsequent delay was a real problem (1). The reason for this in part was the diversity in its presentation. Consequently, we developed the acronym tool “CUBED” to help health professionals feel more confident when assessing and referring suspicious lesions on the foot (2).
Image of the lesion.
(Image reproduced under Creative Commons Licence CC BY-NC-ND 4.0)
As research has shown, around 2-8% of melanoma have little or no melanin pigment within them but unfortunately, on the foot this rate is much higher (possibly closer to 40%) making recognition even more difficult. In a paper published earlier this year by Okhovat and colleagues (3), the authors discuss a case of ALM which previously had been diagnosed as a verruca which was previously treated with cryotherapy. The case presentation made me reflect on something I had learned when assessing tumours on the feet - if you see pink, stop and think!
The published case in this paper was a reporting a 50-year-old man who had had a flesh coloured plaque on the plantar surface for a few years which had suddenly increased in size. The lesion itself was smooth and relatively large measuring nearly 2cms by 3cms. Previously treated as a wart, the lesion was finally biopsied and was confirmed as an advanced amelanotic acral lentiginous melanoma. The lesion was stage 3b. The difficulty in this case was probably the innocuous appearance of the lesion – flesh coloured and smooth. Despite this, lesions which are evolving or growing should always raise suspicion.
The use of dermoscopy can sometimes be helpful here but not always (4) – papers have discussed features of amelanotic melanoma such as milky red areas or abnormal vessels but in this case none of these were evident. The key message here is to monitor such lesions closely and any nodular lesion or plaque which is growing or changing in form, should be treated with suspicion, and melanoma should always be excluded as a possible diagnosis. A firm, enlarging nodule on the sole should be considered a melanoma until proven otherwise.
The full paper of this case report is available to view online (click here):
Full Paper: Okhovat, J., et al. (2019). "A pink enlarging plaque on the plantar foot: amelanotic acral lentiginous melanoma." Dermatology Online Journal 25(1).