The Misdiagnosis of Acral Lentiginous Melanoma: Three Case Presentations

Abstract

Acral lentiginous melanoma (ALM) is a disease that is found on the palms, soles, and nail beds. Because these areas are not often examined during general medical examinations, the presence of ALM often goes unnoticed or the diagnosis is delayed. Research shows that the misdiagnosis of ALM is common, reported between 20% and 34%. We present three cases of ALM that were initially misdiagnosed and referred to the senior author (B.C.M.) in an effort to assess why misdiagnosis is common. The existing literature illuminates clinical pitfalls in diagnosing ALM. The differential diagnosis of many different podiatric skin and nail disorders should include ALM. Although making the correct diagnosis is essential, the prognosis is affected by the duration of the disease and level of invasiveness. Unfortunately, most of the reported misdiagnosed cases are of a later stage and worse prognosis. This review highlights that foot and ankle specialists should meet suspect lesions with a heightened index of suspicion and perform biopsy when acral nonhealing wounds and/or lesions are nonresponsive to treatment.

Acral melanoma mimicking mycotic intertrigo

“…ALM was first described in 1976 by Reed. 3,4 Compared with other subtypes, it is less common in Caucasians and more frequent in higher phototype patients, as demonstrated in our case. 1,4 Interdigital location of ALM is the less common presentation of acral subtype.…”

“…1,4 Interdigital location of ALM is the less common presentation of acral subtype. 3,4 Risk factors general and traditionally described for melanoma, such as sun exposure, phototype, childhood sunburn, and family or personal history of previous melanoma, appear to be less important in acral lesions. 2 Some authors suggest recurrent trauma may be a potential risk factor, but incidence of melanoma is low when compared with the high frequency of trauma in these locations.…”

“…1 Acral lentiginous melanoma (ALM) accounts for 2% to 10% of melanoma cases according to data from the American Cancer Society (2017). 2,3 Plantar regions represent up to 73% of cases, and the incidence is mainly after the seventh decade of life. 2,4 A 73-year-old female patient, phototype III, presented with a complaint of a long-term brownish patch between the third and fourth left toes, with concomitant maceration ( Figure 1A).…”

“…2 Some authors suggest recurrent trauma may be a potential risk factor, but incidence of melanoma is low when compared with the high frequency of trauma in these locations. [2][3][4] A French series of 126 cases found that Breslow thickness, male gender, and amelanosis were significantly associated with worse prognosis. 2 This seems to be worse in ALM because of often-delayed diagnosis.…”

“…However, it is still controversial whether only the histological subtype could be a worse outcome variable. 3 Differential diagnoses that should be considered include warts, callosities, eccrine poroma, fungal infections, foreign body, pyogenic granuloma, inflammatory lesions, bullous disorders, diabetic ulcer, nevi, keratoacanthoma, subungual bruising, and onychocryptosis. 1,3,4 It is worth noting that up to 10% of ALM cases can simulate mycotic intertrigo, 3 reaching diagnostic mistakes up to 20% to 34% in some cases series.…”