Are there different types of melanoma? | | Fig. 45.2 A, Superficial spreading malignant melanoma. The lesion shows asymmetry, notched borders, and shades of light brown. B, Superficial spreading malignant melanoma that has developed a nodular melanoma. C, Acral lentiginous melanoma on the sole of the foot demonstrating a macular and focally nodular pigmented lesion with multiple shades of black and gray with a very irregular border. (Panel A courtesy of James E. Fitzpatrick, MD; panel C courtesy of Fitzsimons Army Medical Center teaching files.) |
There are several different types of melanoma, and each may appear somewhat differently: - Superficial spreading malignant melanoma (SSMM) is the most common form of melanoma in Caucasians (~70% of cases). It is most commonly diagnosed in the fourth or fifth decade. It usually presents as a slowly enlarging, brown (usually) or black spot that may have both a macular and papular component. The lesion may show color variegation and irregular borders (Fig. 45-2A). About 30% arise in a preexisting nevus, and 75% of these lesions demonstrate regression on clinical exam.
- Nodular melanoma is the second most common type of melanoma and represents about 15% to 20% of all cases. It is most commonly diagnosed in men between the fifth and sixth decade. Nodular melanoma usually presents as a pigmented (usually brown or black) papule that slowly enlarges and frequently ulcerates. These lesions most commonly present on the head, neck or trunk. Nodular melanomas may ulcerate, presenting as a nonhealing skin ulcer (Fig. 45-2B).
- Lentigo maligna melanoma, also known as the Hutchinson freckle, represents ~15% of all cases of melanoma. It usually presents as an irregularly shaped, flat, pigmented lesion on actinically damaged skin. It is seen most frequently on the face or other sun-exposed sites. Most patients are in their seventh decade. More advanced lesions can develop papules or nodules, indicating the lesions have developed a vertical or downward growth component.
- Acral lentiginous melanoma represents 5% to 10% of all cases of melanoma. It is the most common form of melanoma in African-Americans, Asians, and Hispanics (Fig. 45-2C). The latter does not reflect an increase incidence of acral lentiginous melanoma in these races. It usually appears as brown or black macules arising on the glabrous (non–hair-bearing) skin of an extremity (palms, soles, or nail beds). It can also occur on mucosal surfaces. The latter have an extremely poor prognosis.
- Amelanotic melanoma is usually considered a non–pigment-producing variant of nodular melanoma. Amelanotic melanoma can be confused with other benign skin lesions, such as pyogenic granuloma. Amelanotic melanoma often evades early diagnosis and results in a poorer prognosis.
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