Case Outline
A 71-year-old white male presented for an assessment at the podiatry clinic describing “a painful corn under his right foot”. He was examined by the podiatrist who noted an unusual vascular lesion / ulcer distal to the metatarsal head on the plantar surface. The patient had no recollection of how long the lesion had been present and denied any pain from the lesion. The podiatrist initially suspected a foreign body and planned a review in two weeks, with a view to a second opinion if was no better at the next appointment.
In the following fortnight, no improvement was noted, and a second podiatry colleague reviewed the lesion. He recorded the possibility of a pyogenic granuloma but without histology other (benign and malignant) tumours could not be ruled out. Consequently, with no clear diagnosis referred the patient back to his GP recommending an urgent review by the skin cancer team under the two-week wait. Despite the immediate action of the podiatrist, he was not reviewed by his GP for 8 weeks. Subsequently, he was referred to the dermatology department for a biopsy. A diagnosis of amelanotic melanoma was made, and the patient underwent sentinel node lymph biopsy to establish if distal spread had occurred. He remains well and under review by the dermatology team.
Amelanotic melanoma - difficult to diagnose
Melanoma continues to be a diagnostic challenge on the foot owing to its late and highly variable presentation. The plantar surface remains the most common location for acral lentiginous melanoma on the hands and feet (1). Lack of visibility and absence of symptoms can lead to a delay in presentation. One study highlighted how the feet are rarely examined during skin surveys conducted by patients (2). In a previous study, the author has shown in a cohort of patients with foot melanoma that it took on average nine months for a patient to seek professional after first noticing a lesion (3). Predictors of late presentation are increasing age, male gender, and a low educational level (4).
A higher rate of amelanosis on the hands and feet
Melanoma diagnosis may also be delayed as the typical brown pigmentation may be limited or completely absent as a higher proportion of melanoma on the hands and feet may be amelanotic (5), as in this patient. Patients presenting with a suspicious tumour should be assessed carefully as evidence has shown that mis-diagnosis rates, particularly in acral melanoma are high.
Implications for Podiatrists
Unusual looking lesions, particularly in older patients, require careful evaluation. When questioning patients, a history of trauma should not exclude the possibility of a melanoma. Evidence suggests many cases of melanoma are brought to the attention of the patient by co-incidental trauma and injury. The role of trauma in the aetiology of melanoma remains controversial, but it may bring the patient's attention to an existing lesion (5). The use of digital photography can be helpful in charting lesions. Dermoscopy has also been shown to improve a clinicians diagnostic ability, including podiatrists (6) - which I have covered in an earlier blog.
Where there is diagnostic doubt a second opinion should always be sought without delay. Typically, this should be a telephone call or letter marked "urgent" sent to the patient’s general practitioner outlining the clinical features and uncertainty of the diagnosis, suggesting an urgent assessment. Good clinical and dermatoscopic images included in the referral. Patients should then be contacted to ensure that they have been followed up.
Thank you to Matthew Bland Owner, M&C Podiatry Ltd, Essex for supplying the case study, with his patients permission.
Dermatology case studies are always welcomed for publication on this website.
References
1. Kuchelmeister C, Schaumburg-Lever G, Garbe C. Acral cutaneous melanoma in caucasians: clinical features, histopathology and prognosis in 112 patients. 2000. p. 275-80.
2. Tsai MS, Chiu MW. Patient-reported frequency of acral surface inspection during skin examination in white and ethnic minority patients. J Am Acad Dermatol. 2014;71(2):249-55.
3. Bristow I, Acland K. 37 cases of acral lentiginous melanoma (poster). British Association of Dermatologists 88th Annual Conference SECC, Glasgow 2009.
4. Richard MA, Grob JJ, Avril MF, Delaunay M, Gouvernet J, Wolkenstein P, et al. Delays in diagnosis and melanoma prognosis (I): the role of patients. Int J Cancer. 2000;89(3):271-9.
5. Bristow IR, de Berker DA, Acland KM, Turner RJ, Bowling J. Clinical guidelines for the recognition of melanoma of the foot and nail unit. J Foot Ankle Res. 2010;3(25).
6. Serra-Garcia L, Podlipnik S, Bedoya J, Ertekin SS, Manubens E, Carrera C, et al. Dermoscopy training course improves podiatrists' accuracy in diagnosing lesions suggestive of acral melanoma: A cross-sectional study. Australas J Dermatol. 2021;63(1):344-e48