A 71-year-old man presented with a 2-year history of a plantar wound under the left fifth meta-tarsal head. The patient was on medication for hypertension, diabetes mellitus, and a cerebrovascular accident (CVA). His left foot and ankle exhibited an equinovarus deformity caused by the CVA 20 years earlier, and the patient reported experiencing recurrent callosity under the fifth metatarsal head. The wound, devoid of clinical signs of wound infection, was pigmented and measured 1.5×3.0 cm (Fig. 1). The blood sugar test (BST) revealed results of 100–196 mg/dL, and the ankle-brachial index (ABI) of the right and left legs were 1.05 and 0.61, respectively. Quantitative sensory testing revealed no signs of diabetic neuropathy. A punch biopsy was performed, and the pathological findings were consistent with malignant melanoma. No metastases were detected on either whole-body positron emission tomography (PET) or chest, abdominal, and pelvic computed tomography (CT). The malignant melanoma was removed using wide lo-cal excision, and the defect was repaired using a skin graft and percutaneous angioplasty (Fig. 1B).

A 68-year-old man presented with an 8-month history of a skin defect on the tip of his left fifth toe, which had initially been dark in color (Fig. 2A). The patient also had a history of hypertension, diabetes mellitus, and hyperlipidemia. Wound dressing was initially performed because the wound exhibited no signs of infection and digital circulation appeared good. However, the wound appeared slightly aggravated after 1 month of conservative treatment. Laboratory testing revealed a BST result of 222 mg/dL, a glycated hemoglobin (HbA1c) level of 8.9%, a C-reactive protein (CRP) level of 0.51 mg/dL, and ABI values of 1.18 (right) and 1.21 (left). While the patient’s digital sensory function was intact, a foot X-ray revealed resorption of the distal phalanx of the left fifth toe (Fig. 2B). As the clinician suspected that the concomitant chronic osteomyelitis of the distal phalanx might impede wound healing, a biopsy was performed with wound debridement and minimal bone resection. Pathological examination revealed poorly dif-ferentiated squamous cell carcinoma with chronic inflammation and bone invasion, but no evidence of metastasis. A toe amputation was performed.

A 75-year-old man presented with a 1-year history of a persistent wound on the nail bed of the right hallux (Fig. 3). The toenail had been extracted spontaneously. Though the patient had developed a diabetic foot wound 3 years earlier after wearing tight shoes, the wound had subsequently healed. Clinical and laboratory examinations revealed no signs of infection, with an initial BST result of 230 mg/dL, an HbA1c level of 7.6%, and ABI values of 1.34 (right) and 1.31 (left). A foot X-ray revealed no signs of bone erosion. The patient reported slightly decreased sensory function, which was not quantitatively tested. A punch biopsy revealed poorly differen-tiated malignant melanoma. A metastatic workup with whole-body PET revealed multiple hypermetabolic lymph nodes at the right inguinal, right external iliac chain, mediastinal pre-vascular, right paratracheal, and left supraclavicular fossa nodes. The patient is being treated using palliative radiation therapy and chemotherapy.

A 78-year-old man presented with a 3-month history of a wound and exudate on his left hallux (Fig. 4). The patient was receiving medication because of diabetes mellitus, hypertension, and CVA. Laboratory testing revealed a BST result of 156 mg/dL, an HbA1c level of 6.1%, and a CRP level of 0.04 mg/dL. A foot X-ray found no bony erosion. Malignant melanoma was diagnosed based on the pathological results from a punch biopsy. No metastatic lesions were detected and a transphalangeal amputation was performed. Three months later, an inguinal mass was detected via palpation, and an ultrasonography-guided gun biopsy was performed to confirm the presence of metastatic malignant melanoma. Metastatic lesions were also found in the liver. Chemotherapy would have been difficult due to the patient’s poor general condition and the rapid progress of the disease. The patient received palliative care and ultimately died 3 months after the detection of the metastatic lesions.

A 77-year-old man presented with a 1-month skin lesion between the left fourth and fifth toes (Fig. 5). The patient was receiving medication because of hypertension, diabetes mellitus, and Parkinson’s disease. The diabetes was well-controlled, and laboratory testing found a BST result of 134 mg/dL and an HbA1c level of 5.7%. There were no clinical signs of infection. A punch biopsy was performed, and the pathological results confirmed the diagnosis of acral lentiginous melanoma. A whole-body PET revealed no evidence of metastatic lesions, and a midfoot amputation was performed.

A 91-year-old man with a 30-year history of diabetes visited our clinic with a 2-year history of a left dorsal foot wound (Fig. 6A). The patient’s medical history only indicated diabetes mellitus and diabetic nephropathy, and his left third and fourth toes had been amputated 20 years earlier because of a diabetic foot wound. At the time of the visit, the wound was hypertrophic and ap-proximately 10×10 cm. Laboratory testing revealed a BST result of 165 mg/dL, an HbA1c level of 6.5%, a blood urea nitrogen level of 30 mg/dL, a serum creatine level of 1.74 mg/dL, and a CRP level of 1.75 mg/dL. Foot radiography showed destruction of the lateral midfoot, which coincided with the location of the wound (Fig. 6B). A punch biopsy confirmed the diagnosis of moderately differentiated squamous cell carcinoma. A whole-body PET detected no metastatic lesions, and the patient subsequently underwent amputation below the knee.

A 35-year-old man with a 2-year history of diabetes mellitus presented with ulceration and an eschar wound on the right foot plantar side of the hallux at the metatarsophalangeal level. The wound started from a bulla formation after walking for a long time, 6 weeks before his visit to the clinic. The size of the wound was 2.3×1.0 cm (Fig. 7A). At the patient’s first visit, a wound biopsy was performed, showing a fragmented normal epidermis with inflammatory exudate. The wound was assessed as a diabetic foot ulcer and managed conservatively with local debridement. However, the wound did not heal for 8 months, even after serial debridement and proper management. Therefore, an en bloc excision of the ulceration and a full-thickness skin graft was performed. The permanent pathology report of the ulceration showed verrucous squamous cell carcinoma. No metastasis was detected by PET or by a chest, abdominal, and pelvic CT. Under combined operation with the orthopedic department, a wide excision was planned, and the plastic surgery team reconstructed the defect with an anterolateral thigh free flap. The wound then healed without any major complications, and the flap was well-maintained for 18 months (Fig. 7B and C).

A 79-year-old woman presented with left foot ulceration on the medial malleolus side. She was on medication for hypertension and diabetes. The wound developed 2 years previously and was managed conservatively at the primary clinic. However, 6 months before the referral, the patient visited a local tertiary clinic for further management as the wound was growing and her pain was worsening. After serial debridement, a full-thickness skin graft was performed with a tissue biopsy which indicated squamous cell carcinoma (Fig. 8A). The patient was referred to our clinic for further evaluation and surgical management. PET imaging and an abdominal-pelvic CT suggested a left-sided inguinal lymph node metastasis. A wide excision of the lesion with inguinal lymph node dissection was performed by the orthopedic team, and a soft tissue reconstruction with a contralateral anterolateral thigh free flap was performed by the plastic surgery team. The wound healed without any major complications and the flap was well-maintained for 1 year (Fig. 8B, C).