Acral Lentiginous Melanoma (ALM)
Acral Lentiginous melanoma accounts for about 5-7% of the melanomas in Caucasians but up to 60% in persons of color (African Americans, Hispanics, Asians, and Native Americans).
It appears mostly on the soles of the feet, but also on the palms of the hand, mucus membranes, penis, and under the nailbeds (subungual). It can be raised and round, flat, dark brown or black, multicolored with irregular edges or unevenly pigmented. Parts of the lesion may be fuzzy and distorted appearing almost bruise-like. ALM has a tendency to open and scab over. Fortunately, growth is generally slow, spreading radially over an average of two and one-half years. Ulceration or nodular growth herald the onset of vertical growth and deep invasion.
Subungual (nailbed) melanoma is less common in the overall reates for melanoma but represents about 33% of melanomas in dark-skinned people. Characteristics include a brown or black linear nail band(s) often wider than 5 mm with a blurred or irregular border with the thumb and big toe being the primary nail site. Approximately half of these tumors may have little or no color leading to a delay in diagnosis. The colored nailband variety can be confused with a fungal infection (especially in the toe) or trauma thus leading to misdiagnosis and/or delay in treatment.
Subungual melanoma generally occurs in the fifth to seventh decades and is rare in children. ALM has both a shorter interval to recurrence and a tendency to recur locally (Zettersten et al, 2003).