Cath Lab Digest

In an article published in the New England Journal of Medicine (NEJM) in 2006, the author gives an account of a 53-year-old female patient who received treatment from a podiatrist for a plantar wart for two years. She underwent electrocoagulation therapy without histological examination.
Her lesion grew and she eventually sought the care of the NEJM author, who biopsied the lesion and noticed enlarged inguinal lymph nodes. The biopsy revealed amelanotic melanoma exceeding 6 mm in thickness (Clark’s level IV). Despite excision of the lesion and involved lymph nodes, and interferon therapy, the patient died six months after presenting.¹
As podiatric physicians, we often encounter various lesions that occur on the lower extremities. The vast majority of these lesions turn out to be benign. Some examples of benign lesions include skin tags, hyperkeratoses and dermatofibromas. Other benign lesions, such as nevi, present with a pigmented appearance.
Nevi can occur as three typical variants: junctional, compound and dermal/intradermal nevi. Junctional nevi present as flat, nonpalpable, hyperpigmented lesions that occur at the dermoepidermal junction above the basement membrane. Compound nevi are most commonly rounded, raised and hyperpigmented. One may see these lesions at the dermoepidermal junction and also within the dermis. Dermal nevi present as round, raised, flesh-colored or pigmented. They occur entirely within the dermis. We also manage and treat many other typical problems such as verruca and ulcers.
When these typical lesions are resistant to care and become chronic non-healing issues, we need to ask ourselves a key question.
Could this lesion be malignant?
The incidence of malignant melanoma has increased over the last few decades. This increase could be attributed to the increase in biopsies performed by physicians as well as an increase of ultraviolet radiation secondary to atmospheric changes.
Melanoma of the foot accounts for approximately 3 to 15 percent of all cutaneous forms of melanomas and, in 7 percent of these cases, they are located on the plantar surface.^2-3 Clark, et al., first classified cutaneous melanomas in 1969 as superficial spreading melanoma, lentigo malignant melanoma and nodular melanoma.⁴ Reed, et al., subsequently described a fourth subtype, acral lentiginous melanoma, which primarily occurs on the plantar and palmar surfaces.⁵

Pertinent Insights On Acral Lentiginous Melanoma

Acral lentiginous melanoma (ALM) is most common among people with darker pigmented skin (such as natives of Asia, India, Africa and African-Americans). It is relatively infrequent in the fairer skin populations.^6,7 Acral lentiginous melanoma is the most common subtype of melanoma that presents on the plantar surface of the foot.³
Due to its unusual site of occurrence, ALM is often misdiagnosed as a wide variety of conditions. These conditions include verruca, hyperkeratoses, onychomycosis, tinea, blisters, keratoacanthoma, onychocryptosis, crusty lesions, ulcerations, sweat gland conditions, non-healing traumatic wounds, foreign bodies, subungual hematomas and nevi.^1,8-14
There are at least two accounts of ALMs that were misdiagnosed as diabetic foot ulcers.^12,14 Also bear in mind that acral lentiginous melanoma may present as an amelanotic lesion and may not exhibit the classic signs of malignant melanoma associated with the mnemonic “ABCD” (asymmetry, border, color and diameter).⁶
Researchers have shown that ALM has a high association with:
• high total body nevus counts;
• nevi on the soles;
• a penetrating injury of the feet or hands; and
• heavy exposure to agricultural chemicals.¹⁵
However, it was interesting to note that the same study showed that current cigarette smoking was inversely related to cases of acral melanoma.