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Malignant melanomas are commonly misdiagnosis on the foot compared to other anatomical areas, the plantar aspect is the most frequently misdiagnosis location (Schade). Often melanomas are misdiagnosed as ulcerations, fungal infections, traumatic injuries, blisters, verrucae and much more.
Misdiagnosed Wart
Schade et al. talks about a 60-year-old white female who presents with a lesion on her bunion deformity. The patient has been self-treating this lesion for over 5 years with over the counter wart and callus topical therapies. The lesion has gotten larger which is when the patient went to her primary care physician who diagnosed the lesions as a “wart” and “irritated bunion” but referred her to a podiatrist for further evaluation. The podiatrist ordered a biopsy for the patient and it came back with a diagnosis of melanoma, nodular type with ulcerations with maximum invasive thickness. There was also lymph node invasion.
The patient had to undergo AJCC Stage III, pT4b, N2, MX and the patient was kept on bed rest for first three days and then slowly transitioned into different forms of casts. In addition, the patient was on adjunctive interferon therapy post treatment. The patient had to be monitored every 3 months and if the results were normal then the patient had to return every four months for the next two years. 36 months after melanoma removal, the patient remains disease free with no recurrent lesions or new areas of concern.
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The authors also mention another case where a 68-year-old male presented with a 2-month skin build up on the plantar medial aspect of the first metatarsal-phalangeal joint of his right foot. The patient was diagnosed with a “wart” and was prescribed topical salicylic acid twice a day under occlusion; the treatment was applied for two months and then was discontinued. Eight months after the initial visit, the patient revisited his primary care physician because he believed the lesion had worsen. A biopsy was ordered, and the patient was diagnosis with nodular pattern melanoma. The patient did not have any erosion or involvement of the first MTPJ and the superficial lymph node resection showed 1 out of 8 lymph nodes was positive for melanoma. Based on the patient’s condition, they were given AJCC Stage III, pT4 pN1a MX and after the treatment the patient declined adjunctive interferon therapy. The patient has remained disease free 16 months after the surgical intervention.
Ulcers
There has a been a lot of debate of trauma being the cause of melanoma, however there is currently no evidence to suggest that trauma causes melanomas. Often, physicians will associate the lesion or ulcer with trauma based on the patient’s history rather than have melanoma high on their differential diagnosis. Gumaste et al. talks about case where 66-year-old white women presents to a dermatology clinic with an ulcer on her left heel which has been present for 1 month. The patient believed that the lesion was due to her dancing barefoot on wooden floors but has noticed that the lesion has not healed. The ulcer had a slight central scale and a focal area of dark pigmentation and the dermatologist recommended wound care with petroleum jelly and occlusion under a bandage.
After four months, the patient returned with a lesion that showed minimal improvement; the patient had the lesion debrided twice and the dermatologist once again recommended intensive wound care with warm soaks, petroleum jelly and bandages. However, the patient returned in one week with concern that the lesion had worsen in which the patient was referred for a shave biopsy. After the biopsy, the patient was diagnosis with ulcerated melanoma and the patient had the melanoma excised as it had clear margins and it was staged at IIIa. The patient also underwent radiation treatment for her popliteal region and at the site of the melanoma.
However, she developed three satellite nodules a year later and was enrolled in a melanoma vaccine clinical trial which improved her condition. Then 1.5 years later, the patient developed multiple in-transit lesions of the lower extremity and underwent isolated limb infusion therapy followed by ipilimumab therapy. The patient currently remains disease free.
Fussell et al. talked about a case where a 74-year-old male presented with a nonhealing wound on the left heel, the wound had been there for two months and he believed that the ulcer was due to stepping on something and his wife believed that his shoes rubbed the heel thus causing the wound. The patient was treated with topical antibacterial cream and Epsom salt soaks but saw no improvement. There is a history of nonmelanoma skin cancer in the patient’s family.
When looking at the patient’s lesion, there is no foot deformity and the wound was irregularly shaped with a dark grayish-purple base. Once the lesion was biopsied, the patient was diagnosed with ulcerated malignant melanoma in the vertical growth phase extending to the epidermal and dermal margins. His melanoma was staged at T3b and a wide local excision was performed. The patient opted out of adjuvant interferon therapy and is currently alive and well with no disease.
The plantar surface is commonly traumatized which can change the appearance of an existing lesion. This makes it harder for the physician to recognize as it does not fit the typical diagnostic criteria for melanoma. Physicians are also hesitant to biopsy the plantar surface because the procedure can cause scarring which can lead to ambulation problems. There can also be additional postoperative problems if the patient has other comorbidities such as venous insufficiency, diabetes, peripheral arterial disease. However, an ulcer that does not heal with treatment should be a sign that the ulcer should be biopsied as delay in diagnosis can lead to a higher stage of melanoma and worse outcomes (Gumaste and Fussel).
Diabetic Ulcers
It is not uncommon for malignant melanomas in the foot to be misdiagnosis in diabetic patients especially if their lesion is small, ulcerated and amelanotic (Gray). In diabetic patients, their ulcers can be attributed to either ischemic necrosis or non-healing diabetic ulcers (Gray, Mansur). There is currently no guideline of when to refer a non-healing diabetic foot ulcer to a specialist, however it is recommended that if there are no risk factors of diabetic foot ulcers or if the patient has adequate patent arterial supply with no infections that a biopsy should be considered (PUT IN CITATION – GAO?).
Gao et al. talks about a 78-year-old patient who presented with ulcers on her right foot for six months. The patient has had type 2 diabetes mellitus for 8 years and it has been poorly controlled. Her ulcers were on the right heel with a pigmented margin and one ulcer had red granulation tissue present. The ulcers were diagnosed as diabetic foot ulcers and the patient received insulin, antibiotics, wound debridement, dressing changes and medication for her neuropathy and peripheral arterial disease. After two weeks, there has been no improvement in her ulcers and a biopsy was performed. She was then diagnosed with malignant melanoma with a Breslow thickness of 1.6 mm with no metastasis. The patient received a wide excision and no other metastasis have been found.
Mansur et al. brings up a case about an 87-year-old diabetic women who presented with a non-healing painless ulcer on her left foot which has been present for 2.5 years. Her type 2 diabetes was well controlled. The ulcer has been managed by local wound care and antibiotics for two years with no improvement. She was diagnosis with a necrotic ulcer on the dorsal surface of her fifth toe and her digit was amputated. This was when physicians noticed multiple papules and nodules on her dorsal foot and the histopathological exam of her amputated digit showed ulcerated nodular melanoma. She was diagnosed with acral melanoma with macroscopic satellitosis. The patient is still under treatment for the melanoma due to her underlying systemic conditions.
Gray et al. talks about a 81-year-old male who presented with an MI but upon physical examination, physicians found a large fungating exophytic mass on his left foot. The patient has a history of diet-controlled type 2 diabetes with signs of peripheral neuropathy and decreased protective sensations but no evidence of peripheral arterial disease. He mentioned that the mass has grown rapidly over four months and that he initial thought it was just a corn. Physicians initially believed that the mass was due to his type II diabetes, however he was later sent for a biopsy. The patient was diagnosed with stage IV malignant melanoma and due to the invasive nature of the disease, he was given palliative care and passed away 18 days later.
