Key Clinical Updates in Malignant Melanoma
Less than 30% of melanoma develops from existing moles.
ESSENTIALS OF DIAGNOSIS
May be flat or raised.
Should be suspected in any pigmented skin lesion with recent change in appearance.
Examination with good light may show varying colors, including red, white, black, and blue.
Borders typically irregular.
Malignant melanoma is the leading cause of death due to skin disease and the fifth most common cancer. The reported incidence of melanoma has doubled over the past 30 years. In 2018, approximately 96,480 new melanomas were diagnosed in the United States, with approximately 60% of cases in men. In 2018, melanoma caused an estimated 7230 deaths (two-thirds in men). One in four cases of melanoma occurs before the age of 40. Increased detection of early melanomas has led to increased survival, but melanoma fatalities continue to increase, especially in men older than 70 years. The lifetime risk of melanoma is 2% in whites, and 0.1–0.5% in nonwhites.
Tumor thickness is the single most important prognostic factor. Ten-year survival rates—related to thickness in millimeters—are as follows: less than 1 mm, 95%; 1–2 mm, 80%; 2–4 mm, 55%. With lymph node involvement, the 5-year survival rate is 62%; with distant metastases, it is 16%.
Primary malignant melanomas may be classified into various clinicohistologic types, including lentigo maligna melanoma (arising on chronically sun-exposed skin of older individuals); superficial spreading malignant melanoma (two-thirds of all melanomas arising on intermittently sun-exposed skin); nodular malignant melanoma; acral-lentiginous melanomas (arising on palms, soles, and nail beds); ocular melanoma; and malignant melanomas on mucous membranes. These different clinical types of melanoma appear to have different oncogenic mutations, which may be important in the treatment of patients with advanced disease. Less than 30% of melanomas develop from existing moles. Clinical features of pigmented lesions suspicious for melanoma are an irregular, notched border where the pigment appears to be spreading into the normal surrounding skin, and surface topography that may be irregular, ie, partly raised and partly flat (Figure 6–5) and eFigure 6–7. Color variegation is present and is an important indication for referral. A useful mnemonic is the ABCDE rule: “ABCDE = Asymmetry, Border irregularity, Color variegation, Diameter greater than 6 mm, and Evolution.” The history of a changing mole (evolution, including bleeding and ulceration) is the single most important historical reason for close evaluation and possible referral. A mole that appears distinct from the patient’s other moles deserves special scrutiny—the “ugly duckling sign.” A patient with a large number of moles is statistically at increased risk for melanoma and deserves annual total body skin examination by a primary care clinician or dermatologist, particularly if the lesions are atypical.
Melanoma resembling a seborrheic keratosis on the lateral face of a man. (Used, with permission, from Richard P. Usatine, MD ...