When an ulcer isn’t what it seems 

Ulceration is a routine finding in patients living with diabetes. When a patient with diabetes presents with a lesion it's easy to make the most common diagnosis: ulceration due to a combination of neuropathy, ischaemia, infection and pressure.  

Most of the time, that instinct is right, but occasionally, it isn't. 

Occasionally, what appears to be a diabetic foot ulcer is actually melanoma. A cancer that is so rare on the foot that it is often overlooked. If it goes unrecognised for any length of time, however, it can have life-shortening consequences. 

To understand why these lesions are missed, the published case reports of melanoma on the foot that had been misdiagnosed in people with diabetes were systematically reviewed.  

The findings, published in the Journal of Foot and Ankle Research, carry an important message for clinicians. Sooner or later, most podiatrists are likely to encounter a melanoma on the foot during their career.  

What the review found  

Our literature review uncovered 20 published cases from 10 countries, spanning 15 years from 2010 to 2025. The pattern across them was strikingly consistent: 

• patients were typically older (around 73 years of age)  

• lesions were found on the heel or forefoot, exactly where a diabetic foot ulcer would be found 

• in 17 of the 20 cases, the melanoma was misdiagnosed as a diabetic foot ulcer 

Melanoma proved to be a great mimic. Diabetic foot ulceration is a plausible, common diagnosis and therefore an easy explanation to settle on.  

A closer look and missing risk factors 

On closer investigation, however, we found that many of these ‘ulcers’ were missing the risk factors that usually predict them in the first place.  

• Only three of the 20 cases had documented neuropathy. 

• Only four had a history of trauma. 

• Lesions often failed to heal despite appropriate off-loading, glycaemic control and dressings. 

• Unexplained bleeding, excess granulation tissue or patchy pigmentation were noted, well before the correct diagnosis was made. 

By the time melanoma was confirmed, the average Breslow thickness was 3.58mm, indicating advanced disease with a poor outcome.  

Worryingly, at diagnosis, seven of the 20 patients already had metastatic disease. 

The real cost of the mimicry is not just a diagnostic miss, but a potentially fatal outcome for the patient. 

Remember ULCER

We undertook an analysis of each case, looking for the common themes that led to the initial misdiagnosis. 

From this we created a simple acronym: ULCER.  

ULCER is intended as a useful series of prompts for the clinician. It is not a diagnostic tool. The acronym spells out the following: 

• Unusual features: spontaneous bleeding, excess or unexplained granulation tissue, or a lesion in a site that doesn't fit a typical ischaemic or neuropathic pattern 

• Longevity: a wound that is static or worsening despite appropriate standard care 

• Colour: irregular or patchy pigmentation in or around the ulcer bed 

• Enlargement: growth or deterioration despite treatment 

• Risk factors absent: no real evidence of the neuropathy, ischaemia, infection or trauma you'd expect to explain the ulceration 

None of these findings alone should trigger alarm since plenty of atypical or slow-healing ulcers turn out to be exactly what they appear.  

But when several of these factors are present together, particularly in a wound that simply isn't behaving the way it should, it's worth pausing before reaching for a repeated round of offloading, dressing and antibiotics. 

Limitations of the review 

This review is based on 20 published case reports and is therefore subject to publication bias. ULCER is intended as an aide-mémoire rather than a validated screening tool and should complement — not replace — clinical judgement and existing diabetic foot guidance.  

Limitations of current national guidance on ulcer management 

After completing this work, we reflected on the current national guidance on diabetic foot ulcer management, including that issued by NICE.  

Current guidance does not prompt clinicians to consider malignancy or recommend a biopsy when a wound fails to heal. This represents an opportunity for future advice to prompt clinicians to consider malignancy when ulcers fail to heal as expected.  

Despite decades of melanoma awareness campaigns across healthcare generally, published literature shows a recurrence of misdiagnosis of melanoma in the diabetic foot due to: 

• lack of suspicion 

• a failure to take biopsies 

Final reflections 

The key message is not that every ulcer could be cancer, but about acting when things just don’t seem right.  

If a diabetic foot ulcer is: 

• unusual in appearance 

• not healing despite everything being done correctly 

• missing the risk factors that normally cause ulceration  

then the lesion deserves a second look. 

Melanoma on the foot is rare. But it is rare in a way that matters. Uncommon enough to be overlooked, yet common enough that most podiatrists are likely to encounter it at some point in their careers.  

Catching it early can make the difference between curative treatment and advanced disease.  

Links and references 

Journal of Foot and Ankle Research. 

About the author 

Michelle Reynolds is a private practitioner with almost 30 years in the profession. She serves on the RCPod’s Special Advisory Group for Dermatology in Podiatry. Her research interests include dermoscopy and its utility in podiatry practice. She is co-author of the systematic review this article is based on, published in the Journal of Foot and Ankle Research.   

Acknowledgements 

Michelle Reynolds would like to thank her co-authors Ivan Bristow and Matthew Young. Thanks also go to Professor Alan Borthwick for his help with the content analysis in the original review.