Temple University School of Podiatric Medicine Journal Review Club

Editor's note: This post is part of the Temple University School of Podiatric Medicine (TUSPM) journal review club blog series. In each blog post, a TUSPM student will review a journal article relevant to wound management and related topics and provide their evaluation of the clinical research therein.

Article title: Malignant melanoma presenting as a foot ulcer.
Authors: Marie-France Kong, DM; Rajesh Jogia, FCPod[Surg]; Stephen Jackson, MRCP; Mary Quinn, MBChB; Paul McNally, FRCP; Prof Melanie Davies, MD.
Journal name and issue: The Lancet, November 12, 2005. Vol. 366 (page 1750).
Reviewed by: Samantha Miner, Class of 2018, Temple University School of Podiatric Medicine.

Melanoma is a cancer of the melanin-producing cells of the skin’s epidermal layer. While it is less common than other skin cancers, it is often considered to be the most dangerous, since metastasis can occur if not detected early. While it accounts for just 4-5% of all melanomas, one type, acral lentiginous melanoma, has a particularly poor prognosis that is associated with misdiagnosis and late detection. Acral lentiginous melanoma is found on the soles, digits, and nail beds of the feet. It has a variegated presentation, but is commonly associated with discoloration, vascularization, and ulceration. As a result, these lesions may mimic the appearance of diabetic foot ulcers. As podiatric physicians, it is important to recognize this type of melanoma in order to improve patient outcomes.

Case Study

A diabetic foot clinic in Leicester, UK reported six cases of malignant acral melanoma over a four-year period. One of these cases involved a 69-year-old type II diabetic male that presented to the clinic with a three-month-old non-healing ulcer under the left first metatarsal head. The ulcer site was extremely painful, despite the patient having peripheral neuropathy. Following ten months of initial treatment with regular debridement, antibiotics, and pressure-relieving footwear, hyper-granulation tissue presented at the edges of the ulcer. Due to its atypical appearance, it was biopsied and determined to be malignant melanoma. The ulcer was then treated with aggressive debridement. However, the patient was subsequently shown to have lymph node involvement and brain metastases, which resulted in his death less than one year later. This clinic also reported an additional five diagnosed cases of acral lentiginous melanoma at their diabetic foot clinic. Of these cases, all were referred to the clinic and two patients did not have diabetes. Further, in the four diabetic subjects all of the melanoma lesions were initially misdiagnosed as diabetic foot ulcers.

Discussion

Despite its low prevalence and curative treatment when detected early, melanoma accounts for 79% of all skin cancer deaths. The most common location to find acral lentiginous melanoma is the plantar aspect of the foot, as was found in this case study. The authors explained that this type of melanoma is often misdiagnosed due to its unusual location and appearance. Unlike other types of melanoma, it does not often have a changing mole pattern, and can even be amelanotic or ulcerated. In addition to non-healing diabetic foot ulcers, other common misdiagnoses include plantar warts, tinea pedis, and hyperkeratoic lesions.

The authors state that four out of the six cases of malignant melanoma were initially misdiagnosed as diabetic foot ulcers in diabetic patients. This fact leads one to infer that a correlation between the development of acral melanoma and diabetes may exist. This may possibly be due to an immunocompromised state induced by diabetes.

Even if there is low clinical suspicion, the authors of this case study emphasize the use of biopsy to improve accurate detection of melanoma. Excisional biopsies are preferred, since they allow for cancer staging and can direct treatment. Despite limited guidelines in the literature on when to biopsy a non-healing diabetic foot ulcer, the authors recommend doing a biopsy early, “if there is no identified apparent cause for delayed healing,” or, “if there is no clinical evidence of arterial disease, and no or minimal sensory impairment.”

Conclusion

Early detection and treatment of acral lentiginous melanoma cannot be stressed enough in improving patient outcomes and prognosis. This case study reported by Kong et al., serves to inform podiatric physicians of their experience in distinguishing this type of cancer from diabetic foot ulcers, as well as to remind them to maintain a high index of suspicion for acral melanoma.

About the Authors:
Samantha Miner is a second-year student at Temple University School of Podiatric Medicine (TUSPM). Samantha graduated from Carnegie Mellon University in 2012 with a Bachelor of Science in Biology and minor in Philosophy. Samantha's interests include the diabetic patient, limb salvage, wound care, and primary podiatric medicine and surgery.

Dr. James McGuire is the director of the Leonard S. Abrams Center for Advanced Wound Healing and an associate professor of the Department of Podiatric Medicine and Orthopedics at the Temple University School of Podiatric Medicine in Philadelphia.