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    The many faces of melanoma

    A review of the major subtypes of melanoma and their features

    During the month of August, Dermatology Times will publish a series of quizzes based on six different case studies by Eve J. Lowenstein, M.D., Ph.D., FAAD, of SUNY Downstate Medical Center in New York, and Kavita Darji, M.D., of St. Louis University Hospital in Missouri.

    Eve Lowenstein, M.D.

    This quiz series aims to review the major subtypes of melanoma and their features to help clinicians refresh their knowledge on melanoma and its variants.

    “Malignant melanoma can present in many different ways and can arise from a pre-existing seemingly benign lesion or de novo. It is crucial for the clinician to accurately identify and treat any suspicious lesion in a timely fashion, as this can help lead to a more favorable prognosis for the patient,” Dr. Lowenstein said.

    The major subtypes of primary cutaneous melanoma include superficial spreading melanoma, nodular melanoma, lentigo maligna and lentigo maligna melanoma, and acral lentiginous melanoma. Of these, superficial spreading melanoma is the most common form, making up approximately 57 percent of all melanomas.

    Melanoma is a malignant tumor originating from melanocytes (most often cutaneous) and responsible for the largest number of skin cancer mortalities worldwide. The different subtypes of melanoma each have their own particular set of characteristics both clinically and histologically, which can impact the treatment and prognosis of the patient.

    “Usually presenting as an asymptomatic brown to black macule with irregular color and borders, superficial spreading melanoma can arise de novo or in approximately one third of cases in the nevus previously present,” Dr. Darji said.

    Nodular melanoma

    The second most common subtype of melanoma is nodular melanoma, representing approximately 21 percent of all melanomas. Nodular melanoma presents clinically as a uniform blue-black, blue-red, or amelanotic nodule, and is the most aggressive subtype with early evolution into the vertical (invasive) growth phase. Lentigo maligna is a melanocytic neoplasm arising on sun-exposed skin of the head and neck, of middle-aged and elderly individuals. According to Dr. Lowenstein, lentigo maligna represents the in situ phase of and can lead to the development of lentigo maligna melanoma.

    Acral lentiginous melanoma

    Acral lentiginous melanoma is most commonly found on the palms, soles and nail beds, and is the most common subtype of melanoma arising in patients of Asian or African descent. It is believed that prior trauma and nevi on the soles and toes could be risk factors for this melanoma subtype. According to Dr. Darji, acral lentiginous melanoma is not associated with sun exposure, and therefore, cannot be prevented in this manner. Since this is the most frequently delayed melanoma subtype to be diagnosed, lesions tend to be more advanced when found Dr. Darji said, and their prognosis is often worse than that of other subtypes of melanoma.

    “As acral lentiginous melanoma is not sun-related, a lot of people don’t think of skin cancer and don’t check their soles for any suspicious lesions on a regular basis, if at all. Here, the clinician has to be sure to check the soles and the between the toes in the skin exam,” Dr. Lowenstein said.

    Subungual melanoma

    Often presenting asrequently occurring on the thumb and hallux. This seemingly harmless nail lesion may gradually develop into a stubbo an black irregular nail bad that changes and widens across the nail, subungual melanoma is an uncommon type of melanoma frn wound, tumor, nail splitting, or nail bed bleeding. According to Dr. Darji, a history of trauma is not uncommonly reported in melanoma nail lesions, and should not be used to discount the possible diagnosis of melanoma. Similar to acral lentiginous melanoma, subungual melanomas are also more common in dark skinned individuals. 

    “Subungual melanomas often present as a melanotic nail band. However, this type of melanoma may sometimes present as a simple nail dystrophy where the patient might not be immediately concerned, leading again to a delayed visit to the dermatologist and a delay in the diagnosis and appropriate therapy,” Dr. Lowenstein said.

    Seemingly innocuous nail dystrophies can sometimes be mistakenly dismissed from consideration for amelanotic melanomas. “These are horrible cases where the delay in diagnosis and treatment can lead to a much worse prognosis,” Dr. Lowenstein added.

    Amelanotic melanoma 

    Apart from desmoplastic melanoma, Dr. Lowenstein said that amelanotic melanoma is probably one of the most difficult diagnoses a clinician has to make because they can easily be clinically mistaken for innocuous lesions like eczema or psoriasis. The early lesions of this type of melanoma frequently show uniform pink or red color, and may have features that overlap clinically and under dermoscopy with non-melanoma skin cancer. These lesions frequently have some identifiable pigment, which can assist in diagnosis.

    Rarely, the features of two lesions may be seen clinically and under dermoscopy, such as seborrheic keratosis and a melanoma. According to Dr. Lowenstein, when presented with such collision lesions that display mixed characteristics indicating two different diagnoses, one’s tendency might be to dismiss the more malignant features for the benign reassuring ones. The lesions that present with mixed features need to be carefully scrutinized with care and when in doubt, a biopsy should be performed.

    “We hope this quiz series will be very informative for clinicians and help them expand their awareness on the different presentations of malignant melanoma,” Dr. Darji said.

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