Acral lentiginous melanoma in situ on the palm with a diffuse parallel furrow pattern

A 47-year-old Black woman reported a concerning discoloration on her left palm present for several years with recent enlargement and darkening.(Fig 1). DERMOSCOPIC APPEARANCEPolarized dermoscopy demonstrated a diffuse ([90%) parallel furrow pattern, a focal lattice-like pattern proximally, and a focal fibrillar pattern distally, along with several shades of brown (Fig 2). HISTOLOGIC DIAGNOSISHistopathologic examination showed increased single unit atypical melanocytes with prominent dendritic processes and increased mitoses, confirming the diagnosis of acral lentiginous melanoma in situ (Figs 3 and4). KEY MESSAGEAlthough the parallel furrow pattern is the major benign dermoscopic pattern seen in acral nevi, a diffuse parallel furrow pattern has previously been described in plantar acral lentiginous melanoma in situ. 1 Despite this typically reassuring finding, concern was heightened by additional dermoscopic features including multiple shades of brown and an overall multicomponent pattern which included a focal fibrillar pattern.Given the absence of mechanical pressure that produces this pattern on the soles, any fibrillar pattern on the palms should be viewed with caution. 2 Additional risk factors included the patient's Fitzpatrick V skin type, age (borderline, [ 50 is high-risk), and lesion size ([7 mm). 1 In summary, pigmented acral lesions with predominantly benign dermoscopic patterns should be approached carefully in the setting of other suspicious dermoscopic findings, suspicious clinical findings, and well-recognized risk factors.Acral lesions are best managed by incorporating both clinical and dermoscopic findings in the context of patient risk factors to avoid missing a malignancy.