TABLE 1.

Malignancies initially suspected to be diabetic foot ulcers (DFU)

Case	Reference	Malignancy type	Age/sex	DM duration (y)	DM complications	Wound description	Misdiagnosis confirmation
1	Black et al 24	Melanoma	73 M	n/r	+	Case of a 73‐year‐old Caucasian male with a 13‐month history of an ungual lesion on his right hallux. Ulcer duration: 13 mo.	“The lesion was initially treated as a chronic diabetic ulceration with failure to resolve with standard of care.”
2	Gaskin et al 25	Melanoma	57 W	2	n/r	A 57‐year‐old overweight woman presented to The Maria Holder Diabetes Centre for the Caribbean with a non‐healing ulcer of the right heel after being treated by various primary care physicians over the preceding year. Ulcer duration: approximately 1 y.	“A 57‐year‐old overweight woman presented to The Maria Holder Diabetes Centre for the Caribbean with a non‐healing ulcer of the right heel after being treated by various primary care physicians over the preceding year. The original debridement sample was not examined by a pathologist. Presumably, at the time, there was no clinical suspicion of melanoma.”
3	Shao et al 33	Squamous cell carcinoma	58 M	n/r	n/r	A 58‐year‐old male patient with diabetic foot ulcer was admitted to the Second Affiliated Hospital of Zhejiang University School of Medicine on December 11, 2018. The patient was treated with local debridement, vacuum sealing drainage treatment, and dressing change and discharged after basic wound healing.	“The patient, a 58‐year‐old male, was admitted to the Second Hospital of Zhejiang University School of Medicine Burn and Wound Repair Clinic (Wound Treatment Center) on December 11, 2018 for a right‐sided diabetic foot ulcer after repeated debridement and dressing changes for more than 1 mo, with recurrent localised redness and pus flow. On the third day after re‐admission to the hospital, he underwent an invasive surgery on the right foot, during which he saw a deep ulcer on the bottom of the foot with localised hairy and brittle basal tissues, which bled easily when touched. The pathological examination on the 3rd day after surgery reported: squamous cell carcinoma of the right foot, keratinized type.” [Translate from Chinese]
4	Novodvorsky et al 37	Lentiginous melanoma	48 M	n/r	−	1‐cm diameter ulcer surrounded by patches of dark brown discoloration within 2‐cm diameter, without signs of infection or callus. Wound duration: more than 4 mo.	Text: “We report a case of a 48‐year‐old man with type 2 diabetes who was referred by his general practitioner to a podiatry‐led foot clinic with a blister over the plantar aspect of the first metatarsophalangeal joint of his left foot. An advice for pressure offloading with a hexagonal shoe was given and he was referred to orthotics for provision of custom‐made insoles and for footwear review.”
5	Suarez Gonzalez et al 36	Melanoma	68 M	n/r	+	Granulated ulcer measuring 4 cm × 3 cm, with no sign of infection.	The paper's title: “Misdiagnosed Malignant Tumour on an Ischemic Limb” Text: “Herein, the authors report the case of a man who presented with melanoma misdiagnosed as an ulcer to draw awareness of the possible resemblance in presentation of ALM to that of an ulcer.”
6	Torrence et al 30	Kaposi's sarcoma	80 M	n/r	n/r	1‐cm diameter painful wound. The tumour cells showed diagnostic positive staining for HHV‐8 (human herpes virus 8). Wound duration: 4 mo.	The paper's title: “A case of mistaken identity: classic Kaposi sarcoma misdiagnosed as a diabetic foot ulcer in an atypical patient” Text: “Classic Kaposi sarcoma is rare in this patient demographic and can be easily misdiagnosed.”
7	Fu et al 34	Mantle cell lymphoma	80 M	n/r	n/r	n/r	Initially, the diagnosis was an infected non‐healing diabetic wound with the possibility of abscess owing to erythema and fluctuance in the affected area. After the MRI assessment, the patient underwent wound biopsy. Pathologic examination of the biopsy specimens showed diffuse proliferation of atypical lymphoid cells. In conclusion, we report the case of a patient who developed subcutaneous nodules and a non‐healing ulcer, which, at first, was treated as a non‐healing diabetic ulcer but later was confirmed to be a skin manifestation of MCL invasion.
8	Gao et al 14	Melanoma	78 F	8	+	Two 0.5‐cm diameter ulcers with pigmented margin. One ulcer with red granulation tissue. A lot of callus around both ulcers, no active drainage, erythema, oedema or other signs of infection. Ulcer duration: 6 mo.	Text: From January 2003 to December 2014, 1132 in‐patients with diabetic foot and 177 in‐patients with ALM were admitted to our hospital. However, one case of them was misdiagnosed as diabetic foot ulcer in this period.
9	Detrixhe et al 13	Melanoma	64 M	n/r	n/r	Ulcerating lesion with an area of blue–brown pigmentation in the periphery of the ulceration.	The clinical hypotheses accompanying the punch biopsies were nodular basal cell carcinoma, fungal intertrigo, keratoacanthoma, lichenoid keratoma (defined as chronically irritated seborrheic keratosis), diabetic foot ulcer. Case 1b (suggested clinical diagnosis was diabetic foot ulcer) was followed by a diabetic foot specialist for several months before dermatological advice for absence of wound healing.
10	Iacopi et al 35	B‐cell lymphoma	76 M	20	n/r	Painful ulcer, wound bed intensively vascularised and partially covered by hyperkeratosis.	Here we report the case of a foot lesion misdiagnosed as DFU but actually caused by diffuse large B‐cell lymphoma
11	Kaneko et al 18	Amelanotic melanoma	80 M	20	n/r	Intractable ulcer. Ulcer duration: 5 mo.	An 80‐year‐old man was referred to our plastic and reconstructive surgery clinic because of a 5‐month history of an intractable ulcer on the left heel. He had a 20‐year history of type 2 diabetes mellitus. Under the diagnosis of diabetic ulcer, for the first half of the year, he received topical therapy with several ointments for the skin ulcer. Nevertheless, the skin ulcer was intractable 2 mo after the initial treatment began, suggesting a different skin condition. By performing an incisional biopsy of an ulcer specimen, a diagnosis of malignant melanoma was made. To the best of our knowledge, four other cases of amelanotic ALM were previously misdiagnosed as intractable diabetic skin ulcers in the initial clinical diagnosis, as in our case.
12	Mansur et al 4	Melanoma	87 F	n/r	+	Painless ulcer that had begun as a dark spot under the nail and small ulcer nearby. Ulcer duration: 2.5 y.	We describe here an elderly female patient treated for a non‐healing foot ulcer interpreted as a diabetic ulcer, which after 2 y was diagnosed as acral melanoma with satellitosis. We describe here a female diabetic patient who presented with acral melanoma with satellitosis masquerading as a diabetic ulcer for 2 y. In our case, because of underlying diabetes mellitus and old age, the ulcer was attributed to ischaemic necrosis due to microangiopathy, precipitated by diabetes and atherosclerosis. As the physicians taking care of the patient were not dermatologists, the nature of the ulcer was not recognised properly. Moreover, although our patient had been having satellite lesions on the foot for nearly a year, neither the patient nor the physicians paid attention to them.
13	Park et al 32	Squamous cell carcinoma	57 M	n/r	n/r	Tender shallow, oval‐shaped, 0.7 × 0.3‐cm ulcer with purulent discharge. Ulcer duration: 6 mo.	We gave oral antibiotics with wound dressing, under the clinical impression of a DM foot ulcer accompanying secondary infection and lymphadenitis. Despite 6 weeks of treatment, a new tender erythematous patch with swelling was discovered on the right thigh. A skin biopsy was performed on the right thigh and was reported as consistent with cellulitis. We switched the oral antibiotic to levofloxacin, but the lesion showed no improvement over 2 weeks. Therefore, we decided to perform another skin biopsy on the right fifth toe. The histopathologic findings showed infiltration of atypical pleomorphic cells with hyperchromatic nuclei, with invasion into the dermis. In our case, as the patient had ulceration with purulent discharge, he received conservative management including wound dressing and oral antibiotics under the diagnostic impression of DM foot ulcer with secondary infection. However, the lesions did not respond to this treatment, and after a skin biopsy of the toe and additional evaluation, we made the correct diagnosis of SCC of the toe.
14	Zaidi et al 26	Melanoma	67 M	9		Diabetes has been linked with malignancies like colon, rectum, liver, biliary tract, pancreas, kidney, leukaemia and melanoma. Melanoma can sometimes manifest as a diabetic foot ulcer. We describe an elderly male with type 2 diabetes, who had presented to us with a non‐healing wound at the right heel, that later turned out to be an invasive malignant melanoma.	“Melanoma can sometimes manifest as a diabetic foot ulcer. We describe an elderly male with Type 2 diabetes, who had presented to us with a non‐healing wound at the right heel, that later turned out to be an invasive malignant melanoma.”
15	Sivaprakasam et al 29	Kaposi's sarcoma	70 M	n/r	n/r	Purplish nodules.	Personal communication.
16	Hussin et al 17	Melanoma	52 F	15	+	Ulcer size 3 × 3 cm, hyper‐granulating base, the skin surrounding the ulcer was pigmented, and there were no signs of local infection. Ulcer duration: 4 mo.	We present two patients with diabetes mellitus and malignant melanomas of the foot initially diagnosed as DFU. A 52 y old Malay woman presented with a non‐healing ulcer of 4 mo duration. She had type 2 DM for 15 y on oral medication. She sustained a small puncture wound on the sole of her left foot from stepping on a sharp object. This ulcerated and was seen by her family doctor who diagnosed a DFU.
17	Koo et al 28	Kaposi's sarcoma	88 M	12	+	Hypergranulating wound exuding serous exudate, asymmetrical in shape, atypical in appearance.	88‐year‐old male with type 2 diabetes mellitus, presented at Liverpool Hospital High Risk Foot Service with a non‐healing wound on his right foot. The patient presented with a plantar wound on his right foot, which had the appearance of a neuropathic ulcer, possibly relating to his diabetes.The presenting lesion in this case was diagnosed on referral as a neuropathic foot ulcer. Due to the similarity classic Kaposi sarcoma has with other conditions, preliminary misdiagnoses could have been: pyogenic granuloma, nodular melanoma, melanocytic nevi or arteriovenous malformations.
18	Thomas et al 22	Melanoma	81 M	n/r	n/r	Painful ulcer with foul smelling drainage, size 6 × 5 cm. The ulcer was necrotic, black with bleeding and minimal purulent drainage.	The patient was started on oral antibiotics with local wound care and surgical consultation requested. Outpatient surgical evaluations showed a black eschar with punctuate areas of bleeding after the removal of the eschar. The patient was admitted to the hospital for surgical debridement of the presumptive diabetic necrotic ulcer.
19	Tomešová et al 38	Melanoma	60 M	6	−	The paper describes a history of a male diabetic patient with an atypical course of the foot defect.	“The defect was considered and treated as DFU for almost 4 mo. Atypical was the pain of the terrain defect of diabetic neuropathy, the absence of signs of inflammation, the appearance of the defect and non‐healing in complex treatment. All these atypics could lead us to a correct diagnosis [malignant melanoma]”. [Translate from Polski]
20	Guarneri et al 16	Melanoma	86 M	30	−	Painless ulcer, size 2.5 × 1.9 cm, slightly hyperkeratotic, partly ulcerated mass with no peripheral erythema, warmth or tenderness on palpation in the surrounding area.	The tumour was diagnosed as a diabetic foot ulcer by both his general physician and an orthopaedist and managed with regular debridement, systemic antibiotics and pressure‐relieving footwear. Incisional biopsies of the lesion were obtained, and histopathological examination showed the dermis to be diffusely infiltrated by a malignant ulcerated mass. In the present case, the initial verrucous appearance of the lesion had favoured its misdiagnosis as a small plantar wart. Later, the ulceration, referred to an accidental trauma by the patient, and the slow healing were disregarded by the general physician because of the diabetes and the concomitant immunosuppressive regimen.
21	Torres et al 8	Melanoma	54 M	n/r	n/r	Painless ulcer, 2.5 cm diameter with pigmented macule, with irregular borders in margins. Ulcer duration: 12 mo.	A 54‐year‐old male patient, with type 2 diabetes mellitus, was referred to our department with a painless, non‐healing ulcer of 12 mo duration under the right fifth metatarsal bone. The ulcer had been managed for months as a diabetic foot ulcer with local wound care, antibiotics and pressure‐relieving footwear.An incisional biopsy was taken from the lesion and the histopathological examination showed a malignant melanoma with a Breslow depth of 5.3 mm.
22	Caminiti et al 27	Kaposi's sarcoma	83 F	n/r	+	Roundish lesion (measuring approximately 15 mm in diameter). The lesion showed keratotic but not undermined edges; the ulcer had mushrooming granulation tissue.	In this report, the authors describe the case of a patient with Kaposi's sarcoma that was initially misdiagnosed as a plantar ulcer.
23	Pereyra‐Rodríguez et al 20	Melanoma	58 F	n/r	+	Ulcer size 4 × 1.5 cm, slightly hyperpigmented nodule with a central ulceration. Wound duration: 7 mo.	The patient had been seen several times by a primary care physician and received topical antibiotic treatment for the presumptive diagnosis of mal perforans from a diabetic neuropathy. When examined, a 4 × 1.5 cm slightly hyperpigmented nodule was found with a central ulceration located on the distal portion of the left foot sole. An incisional biopsy was obtained which included a focus of dark pigmentation. Histological examination showed tumoural melanocytic cell nests filling and expanding the papillary dermis with atypical mitosis and melanoma cells infiltrating up through the epidermis.
24	Kong et al 31	Squamous cell carcinoma	73 M	n/r	+	Painful ulcer discharging pus. Ulcer duration: 7 mo.	73‐year‐old Caucasian man with type 2 diabetes was referred with a 7‐month history of an ulcer on his left heel. His left heel had ulcerated on two previous occasions as a result of fissures and using his heel to prop himself up in bed. The ulcer was superficial and initially showed signs of healing, but it subsequently became very painful and began to discharge pus. A biopsy from the surgical debridement showed moderately differentiated squamous cell carcinoma (SCC). We have previously reported cases of malignant melanoma diagnosed in patients referred to our foot ulcer clinic (4,5); five of seven patients had diabetes, and their ulcers were initially thought to be diabetic foot ulcers, as was the case in this patient.
25	Rogers et al 21	Melanoma	48 M	n/r	n/r	Painless ulcer with mushrooming granulation tissue and areas of intact epidermis in a lenticular fashion over the wound bed. Wound duration: 18 mo.	A male patient aged 48 y with type 2 diabetes presented with a painless non‐healing ulcer of 18 mo duration under his right first metatarsal head. The ulcer was not a typical appearing neuropathic foot ulcer and had mushrooming granulation tissue and areas of intact epidermis in a lenticular fashion over the wound bed.An incisional biopsy was taken from the foot lesion, which showed a poorly differentiated melanoma covered by an intact epidermis and granulation tissue.
26	Yeşil et al 23	Amelanotic melanoma	71 M	17	−	Painless ulcer, 4 cm diameter, no erythema, tenderness or warmth on palpation in wound area.	A 71‐year‐old male patient with a 17‐year history of type 2 diabetes mellitus presented to our clinic with atypical hypergranulation and painless ulcer under his left fifth metatarsal head. He was previously admitted by another physician, and the lesion was diagnosed as a diabetic foot ulcer. He went on to have an incisional punch biopsy of his left foot ulcer, which showed the dermis to be diffusely infiltrated by malignant tumour, displaying melan‐A positivity. The diagnosis was malignant melanoma.
27	Kong et al 19	Melanoma	69 M	2	+	Painful ulcer, atypical hyper‐granulation around edges of the ulcer Wound duration: 2 mo This article describes four cases of melanoma misdiagnosed as DFU, but the characteristics of the patients are presented for only one case.	He had developed the ulcer in January 2003, and had been receiving podiatry care in the community. In addition to this patient, we have diagnosed five other cases of malignant melanoma over the past 4 y which were referred to our diabetes foot ulcer clinic. Two of the patients did not have diabetes. In four of our patients who had diabetes, the lesion was initially misdiagnosed as a diabetic foot ulcer.
28	Gregson et al 15	Amelanotic melanoma	76 F	15	+	1‐cm diameter non‐pigmented ulcer with callus‐like periphery. Wound duration: 15 y.	We report a case of amelanotic malignant melanoma, which presented late due to the ulcer being falsely attributed to diabetes. The diagnosis was missed despite the patient having seen diabetic, vascular and orthopaedic specialists.