This paper presents a case of an early malignant transformation of untreated ulcers in a patient with diabetes. This case shows that Marjolin's ulcer can occur not only after chronic injury, but can also develop in the early stages after the onset. Hence, an early biopsy for diabetic foot ulcers that fail to heal with acute treatment can enable an earlier diagnosis and treatment without amputation, resulting in a better quality of life for the patient.