Malignant Melanoma Misdiagnosis in the Diabetic Foot. What Can We Learn From the Published Literature?

BACKGROUND: The foot is an independent risk factor for a poorer prognostic outcome in melanoma. Delayed diagnosis may arise because melanoma mimics other benign diagnoses, such as ulceration on the foot, including those with associated with diabetes. Improving outcomes for patients includes raising awareness amongst professionals involved in diabetic foot care. Evaluation of published case studies may help identify common themes to inform practice and improve recognition and referral for lesions requiring biopsy. METHODS: The authors undertook a systematic literature search of PubMed (National Library of Health) (2010-2025) to identify published case studies reporting delayed diagnosis or misdiagnosis of melanoma arising on the skin of the foot or in the toenail in patients with diabetes. Data were collated and tabulated to give basic demographics and assist in identification of common themes. A structured content analysis was undertaken to inform key aspects regarding missed diagnosis. RESULTS: Following a systematic search of the literature, 1485 papers were identified. After removal of duplicates and irrelevant papers, a total of 86 case studies were identified. A total of 20 cases were reported in patients with diabetes (reported in 19 papers) from 10 countries, including 14 males and 7 females (average age 73 years), with a mean Breslow thickness of 3.58 mm. Melanoma lesions were located on the heels (n = 8), forefoot (n = 5), toes (n = 3), subungual regions (n = 2) and in the arch (n = 2). The most common misdiagnosis was a diabetic foot ulcer (n = 17). CONCLUSION: Based on the reviewed cases, distinguishing melanoma from diabetic foot ulceration (DFU) is difficult. Common themes from the content analysis suggest that clues such as ulceration despite lack of the corresponding risk factors, hypergranulation and lack of improvement to be key aspects to suggest an alternative diagnosis. The authors propose a simple acronym, 'U.L.C.E.R', as an aide-mémoire to assist healthcare professionals in the identification of potential melanoma masquerading as DFU.