Acral lentiginous melanoma is seen on the palms, soles and under the nails. This is the most common type of malignant melanoma in asians, african and north american blacks, but is relatively infrequen…
Acral lentiginous melanoma is seen on the palms, soles and under the nails. This is the most common type of malignant melanoma in asians, african and north american blacks, but is relatively infrequent in Caucasians. These lesions are usually located on palmar, plantar and subungual skin. Macroscopically, the lesion presents as pigmented and ulcerated plaques or nodules. A tendency for this lesion to be expressed in spindle cell patterns in vertical growth components is one of the distinguishing characteristics. The clinical features are less striking than in other melanomas, appearing in the radial growth phase as macules: dark brown, blue-black, or black, with little variegation and often ill-defined.
This type of melanoma occurs on non hair baring surfaces of the body which may or may not be exposed to sunlight. It is also found on mucous membranes. Acral lentiginous melanoma occurs predominantly in the sixth, seventh, and eighth decades of life, with a peak incidence in the seventh decade for males and in the sixth decade for females. It also occurs in Caucasians and in young people. It does not appear to be linked to sun exposure. It occurs most often in older males and often grows slowly over a period of years. The delay in development of the tumor is the reason these tumors are often discovered only when nodules appear or in case of nail involvement, the nail is shed, therefore, the prognosis is poor.
The most common sign is a brown or black discoloration under the nail bed without a history of trauma. Acral lentiginous melanoma is characterized by lentiginous and some nesting proliferation of atypical melanocytes. The tumour has a radial growth phase. Focally, pagetoid spread is present, however this is not as prominent as in superficial spreading melanoma. The melanocytes may be surrounded by a halo giving a lacunar appearance. It usually starts with a large lesion of 3 cm or larger on the sole of the foot. It looks first like a tan or brown flat stain, appears disorganized with irregular borders. In more than 75% of these cases the growth occurs under the big toe or the thumb. Dark skinned patients develop this much more often.
Many cases of acral lentiginous melanoma are significantly more frequent among non-whites and the elderly, with the primary lesion, on average deeper and ulcerated, without significant differences in the stage or the time elapsed between noticing the neoplasia and seeking the physician. Diagnosis of Acral lentiginous melanoma during the radial growth phase is often difficult, and it may not be recognized initially, but treatment in this phase offers an excellent prognosis. Usually, the clinical and pathological diagnoses are similar, but in cases of thin melanomas that are invasive or ulcerated, the pathological diagnosis will be more reflective of the true situation. Wide local excision with lymph node dissection is recommended for subungual melanomas measuring more than 1.00 mm and for lesions showing severe regression.
Acral Lentiginous Melanoma, Radial Growth Phase, Acral Lentiginous, Lentiginous Melanoma, Radial Growth, Growth Phase