Malignant Melanoma Masquerading as a Decubitus Heel Ulceration

Malignant melanoma is currently the seventh most common form of cancer in the United States. Considered to be the most serious form of skin cancer, the incidence of cutaneous melanoma continues to escalate annually. More than 55,000 new cases were identified in 2004, responsible for the death of nearly 8,000 individuals.¹
Although cutaneous melanoma may appear anywhere on the body, up to one-third of all lesions occur in the lower extremity. The foot is the second most common overall area for presentation.^2,3
Cutaneous melanoma typically arises from melanocytes at the dermal-epidermal junction. More than 50% of these lesions arise de novo without a precursor melanotic nevus.^4–9 During the early stages of growth, melanocytes are typically confined to the epidermis or upper dermis and execute a (radial) horizontal growth phase. When the lesion is confined to the epidermis, the term melanoma in situ is used. Radial growth phase melanomas are associated with a low rate of metastases and are divided into 3 morphologic groups based on clinical and microscopic characteristics.
Superficial spreading melanoma is the most frequent type, characterizing up to 70% of all lesions.^4–9 This type may appear on any body surface. The lentigo maligna type accounts for up to 10% of all lesions and is most commonly found on sun-exposed areas.^4–9 Finally, acral lentiginous melanoma is the least common type of radial growth phase pattern. These lesions appear flat but may be deeply invasive and have been associated with a poor prognosis.^4–9
Clinical distinction between benign and malignant pigmented lesions is difficult and frequently based on speculation, perhaps in association with some type of atypical presentation. Cutaneous lesions should be observed for asymmetry, border, color, diameter, and elevation for irregularities. A persistently changing mole, a family history of melanoma, immunosuppression, and a preexisting nevus are all factors that should warrant clinical consideration.^5,6 In the case of a suspicious lesion, an excisional biopsy with evaluation by a dermatopathologist is required to classify the lesion.
Traditionally, prognosis associated with malignant melanoma has been determined by the anatomic level of invasion (Clark’s level) as well as the overall maximum depth of invasion (Breslow’s thickness).^8,9 Greater awareness and a surge in published data analyses from melanoma treatment centers has facilitated the arrangement of a more specific staging classification with more accurate prognostic indicators.¹⁰ The current tumor-node-metastasis (TNM) classification developed by the American Joint Committee on Cancer (AJCC) is based on tumor thickness, ulceration, lymph node metastases, and distant organ metastases. Following their comprehensive review, the AJCC Melanoma Staging Committee determined that increased thickness, ulceration, multiple lymph node metastases, and distant visceral organ metastases were all strong predictors of a poor outcome.¹⁰

Case Report

A 74-year-old white man presented to the authors’ foot wound clinic with a nonhealing ulcer on the right heel. The patient had a past medical history significant for hypertension and type 2 diabetes mellitus complicated by peripheral neuropathy. Noninvasive vascular exams returned within normal limits. The patient believed that his wound was related to a persistent shoe irritation that deteriorated into ulceration secondary to his peripheral neuropathy. Prior to his presentation at the clinic, he had been treated for more than 6 months at a different wound care center. His previous wound care regimen had consisted of periodic sharp debridement as well as a large variety of topical medications and products including an accommodative shoe. The wound had been complicated by 2 previous episodes of cellulitis treated with oral antimicrobial medication. The patient was concerned with the apparent lack of reduction in wound size and was referred to the clinic at the request of his primary physician.
At presentation, the wound appeared to be a typical decubitus type heel ulceration measuring 2.4 cm x 2.0 cm with a granular, healthy appearing wound bed (Figure 1). The wound was located at the lateral aspect of the patient’s right heel. There was no active drainage, erythema, edema, or other signs of infection present. There was complete loss of sensation at the wound site.
A conservative routine of dressings and enzymatic debridement was the initial treatment plan recommended to the patient. However, the patient was interested in a more aggressive approach and was offered application of an allograft dermatological matrix scaffold (Graftjacket®, Wright Medical Technology Inc., Arlington, Tenn). The procedure was performed 2 days after his initial presentation. During his fifth dressing change, the allograft product inadvertently separated from the underlying wound. Nevertheless, he was advised to continue with local care as previously described. Two weeks following the graft separation, the patient complained of increased drainage and erythema at the wound site. The remaining portion of the graft was removed.
The ulcer site was reevaluated. The underlying tissue remained completely granular with a healthy, viable, and clean appearance. However, the ulcer had increased in size to 5.2 cm x 4.0 cm. A tissue biopsy was taken because of the peculiar situation that had transpired including the previously stagnant nature of the ulcer. Histological examination revealed a malignant melanoma involving the reticular dermis (Figure 2). A strong positive cytoplasmic reactivity was found to HMB45, which is an immunohistochemical marker associated with melanotic differentiation (Figure 3). The patient was referred to the oncology clinic, and a full body positron emission tomography (PET) scan demonstrated increased uptake in the right heel and the right popliteal, hemipelvic, and retroperitoneal lymph nodes with early bony involvement in the ribs. A CT-guided needle biopsy of his right pelvis confirmed these findings, and a bone scan identified metastatic activity in multiple rib segments.

Discussion

This case report illustrates an atypical presentation for a malignant melanoma lesion masquerading as a neuropathic diabetic foot ulcer. The patient had been treated for a considerable amount of time with what could be considered standard care for decubitus foot ulceration. The lesion had apparently been complicated by infection, which further obscured any clinical suspicion of atypical activity.
At presentation to the clinic, the lesion appeared to be a viable and healthy wound that initially was regarded as uncomplicated. A failed allograft procedure prompted a soft tissue biopsy to exclude any uncommon sources of pathology.
This report provokes concern about the use of soft tissue biopsy in the typical wound. Although rare, malignancy has previously been shown to “masquerade” as neuropathic foot ulceration.^11–13 It is common for a wound clinic to treat neuropathic patients and observe only minimal (if any) improvement in wound quality. It would not be feasible to routinely screen for malignancy in each of these individuals. Gregson and Allain¹¹ recently discovered malignancy in a wound with similar presentation. Their report indicates that the patient was treated for neuropathic plantar foot ulceration by multiple medical specialties for more than 15 years with minimal improvement in wound characteristics. Biopsy revealed malignant melanoma, and the patient died soon after the diagnosis was made. Gregson and Allain¹¹ then suggested that biopsy should be performed in cases of nonhealing diabetic foot ulceration in the absence of limb ischemia.

Conclusion

The authors support the recommendations of Gregson and Allain and maintain that soft tissue biopsy should be performed in patients with nonhealing ulcerations of 6 months duration or longer in order to exclude malignancy.