Acral melanoma, specifically of the toes, remains severely underdiagnosed and carries a poor prognosis. Accordingly, these authors emphasize the importance of prompt diagnosis in a case study involving an 81-year-old patient with excessive bleeding from an ulceration on the distal aspect of her left fourth toe.
Although cutaneous melanoma has increased in incidence 4.1 percent yearly worldwide, it remains severely misdiagnosed in the foot and ankle at a frequency as high as 25 to 36 percent.1-7 In addition, prognosis is poor for melanoma in general. Melanoma comprises four percent of all skin cancers but is responsible for 79 percent of all deaths.6,8 Additionally, the five-year survival rate for melanoma of the foot is much lower than melanoma found elsewhere on the body. The survival rate is as low as 16 percent in patients with lymph node metastases.1,9 Early detection is essential both for improving prognosis and avoiding major amputations.4
However, multiple factors can confound swift diagnosis. These factors include:
• a hypopigmented and amelanotic appearance;
• concomitant diabetes and diabetic foot ulcers;
• lack of ABCDE (asymmetry, border irregularity, color, depth and enlargement) characteristics;
• increased thickness without rapid changes in appearance, mimicry of other tumors; and
• the patient’s skin color and/or quality.4-7,10,12,13
Such mimicry to benign lesions may cause some patients to delay self-treatment or seeking medical assistance. Often, these patients do not adequately recognize indications of malignancy such as ulceration, bleeding and increasing lesion size. Diagnosis can be delayed an average of 4.8 years in patients who self-diagnose in comparison to seven months for patients diagnosed by their physician.12
Diagnosing A Nodular Lesion and Subsequent Ulceration On The Toe Of A Patient With Multiple Comorbidities
In a recent case, an 81-year-old female patient with a past medical history of Crohn’s disease, small bowel obstruction, hypothyroidism and hypertension noticed a nodular lesion with subsequent ulceration to the distal aspect of her left fourth toe. The distal toe was an area of high pressure and shear stress due to the contracted position of the toe, increasing the load on the distal tip. She dressed the ulcer with antibiotic ointment and an adhesive bandage daily.
She scheduled an initial appointment with a podiatrist two weeks after initial recognition of pathology by the patient when the ulcer began bleeding excessively. She was initially diagnosed with a pressure sore and was treated with local wound care. Before her next appointment, however, she was admitted to the hospital with an acute small bowel obstruction. The treating physician placed the patient on metronidazole, hydrocortisone and ondansetron to treat the obstruction. The podiatry team was consulted to treat the toe as there was concern that the ulcer was a source of infection and the patients was subsequently seen by the podiatry service to assess the ulcer shortly after admission.
On physical examination, the lesion appeared red, raised and circumscribed. There was a small, bleeding partial-thickness ulcer at the superior aspect without pruritis but tender to palpation. The ulcer did not show any signs of infection. There erythema, edema, purulence or fluctuance. After determining the patient had palpable pulses and epicritic sensation intact, we performed a shave biopsy of the lesion and applied antimicrobial ointment and a dry sterile dressing.
The preliminary diagnosis was pressure ulcer with an intention to rule out hemangioma or other soft tissue tumor. Subsequent histopathology revealed a malignant melanoma, stage pT1b at a minimum. The specimen was S100 and Melan A positive and p63 negative. The podiatry team notified her original podiatrist. The patient had surgery to treat the bowel obstruction and was discharged.
For the melanoma, we referred the patient to a surgical oncologist, who performed an amputation of the left fourth toe at the level of the proximal interphalangeal joint less than six weeks after diagnosis. The pathology examination revealed a retained T4 malignancy with 1 cm clear margins. Positron emission tomography (PET) imaging confirmed no metastasis to the lungs, thyroid and lymph nodes.
The patient returned to her podiatrist almost a year after this definitive treatment. Her podiatrist noted new onset erythema and blistering of the distal amputation site and obtained a biopsy to confirm return of the melanoma. The biopsy sample was positive for recurrent invasive melanoma affecting bone. The patient underwent a left fourth toe amputation at level with the base of the proximal phalanx. The surgery was performed by the patient's surgical oncologist, who sent bone and soft tissue samples to pathology. The patient will continue to see her oncologist for further treatment and monitoring.
What You Should Know About Malignant Melanoma And Wound Mimicry
One in 74 Americans will be diagnosed with melanoma in his or her lifetime.1,9 Up to 15 percent of all cutaneous melanomas occur on the foot and carry a poorer prognosis than melanoma elsewhere on the body.1,9 The diagnosis of acral malignant melanoma can be exceedingly difficult, especially when it presents as a non-pigmented, raised lesion masquerading as an ulcer, fibroma or hemangioma as was the case with this patient. Studies have shown that as much as 94 percent of plantar melanomas are located in areas of higher mechanical stress and weightbearing such as the forefoot and rearfoot, secondary to repetitive trauma.6,7,15
This patient developed ulcerated melanoma at the distal plantar aspect of the toe, an area of high stress with ambulation. Most likely, the melanoma developed much earlier than the initial presentation as the lesion was already ulcerated and bleeding. Ulcerated tumors tend to be thicker than non-ulcerated tumors and ulceration is an independent factor associated with distal metastases and poorer prognosis.12,13,16 Misdiagnosis and delayed treatment of palmoplantar tumors are associated with increased tumor thickness and a five-year survival rate of 15.4 percent versus 68.9 percent in all other areas of the body.1,13,17
Although amelanotic/hypomelanotic melanomas constitute only two to eight percent of all primary melanomas, a higher percentage are Clark level IV melanomas that have a rapid vertical growth phase.3,18-20 The nodular type of melanoma exhibits deep margins in 44 percent of cases versus five percent of the other types (superficial spreading, lentiginous).3,10 Our patient demonstrated a red (amelanotic), ulcerated, bleeding malignancy that the patient self-diagnosed as a simple wound and the podiatry team preliminarily diagnosed as an ulcer with intent to rule out hemangioma.
Shave biopsy was the appropriate next step because excisional biopsy with a one to two cm clean margin would have resulted in partial or total amputation of the toe when malignancy had not yet been confirmed. Fortunately, shave biopsy only delayed treatment by a few weeks. Furthermore, identification of malignancy within two weeks of initial presentation as well as expert and efficient intervention within six weeks may well have prevented further metastasis. With the incidence of melanoma increasing in an aging population, rapid diagnosis of malignant melanoma with suitable treatment is essential along with careful and meticulous follow up care.
Dr. Perry is the Chief Resident of Clinical Education with the Englewood Hospital Podiatric Medicine and Surgery Residency in Englewood, NJ.
Dr. Yuan is in private practice in Manhattan and Brooklyn, NY.
Dr. Demoleas is board-certified by the American Board of Podiatric Surgery and American Board of Podiatric Orthopedics. He is in private practice in Old Tappan, N.J. and Ardsley, N.Y.
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- Mansur AT, Demirci GT, Ozel O, Ozker E, Yıldız S. Acral melanoma with satellitosis, disguised as a longstanding diabetic ulcer: a great mimicry. Int Wound J. 2016;13(5):1006-1008.
- Yeşil S, Demir T, Akinci B, Pabuccuoglu U, Ilknur T, & Saklamaz A. Amelanotic melanoma misdiagnosed as a diabetic foot ulcer. J Diabetes Complications. 2007;21(5):335-337.
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- National Cancer Institute. SEER Cancer Statistics Review, 1973-1999. Available at: https://seer.cancer.gov/archive/csr/1973_1999/. Accessed September 6, 2019.
- McClain SE, Mayo KB, Shada AL, Smolkin ME, Patterson JW, Slingluff Jr CL. Amelanotic melanomas presenting as red skin lesions: a diagnostic challenge with potentially lethal consequences. Int J Dermatol. 2012;51(4):420-426.
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- Rogers LC, Armstrong DG, Boulton AJ, Freemont AJ, Malik RA. Malignant melanoma misdiagnosed as a diabetic foot ulcer. Diab Care. 2007;30(2):444-445.
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- Balch CM, Soong S, Gershenwald JE, et al. Prognostic factors analysis of 17,600 melanoma patients: validation of the American Joint Committee on Cancer melanoma staging system. J Clin Onc. 2001;19(16):3622-3634.
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