In this report, the authors describe the case of a patient with Kaposi's sarcoma that was initially misdiagnosed as a plantar ulcer. The ulcer typically appeared as a neuropathic foot ulceration located on the plantar aspect of the first metatarsal head. There was hyperkeratosis on the plantar surfaces of the other metatarsal heads. However, the lesion had mushrooming granulation tissue, without undermined perilesional edges. A wound biopsy revealed the presence of Kaposi's sarcoma. The presence of cancerous lesions on the plantar aspect of the foot is an infrequent event in diabetic patients. However, given the malignant nature of some skin cancers careful clinical examination and biopsy of the wound are advisable.