Asymmetry: Half the lesion does not match the other half.
Four major subtypes of primary cutaneous melanoma have been identified:
- melanoma is most common on the trunk in men and women, and on the legs in women. It is most commonly seen in individuals aged 30-50 years. It manifests as a flat or slightly elevated brown lesion with variegate pigmentation (ie black, blud, pink, or white discoloration). It is generally greater than 6 mm in diameter, irregular, and with asymmetric borders.
- occurs in 15-30% of patients. It is most commonly seen on the legs and trunk. Rapid growth may occur over weeks to months. This subtype is responsible for the most thick melanomas. It manifests as a dark brown-to-black papule or dome-shaped nodule, which may ulcerate and bleed with minor trauma. It may also be amelanotic. It tends to lack the typical ABCDE melanoma warning signs and may elude early detection.
Lentigo maligna melanoma
- is typically located on the head, neck, and arms (chronically sun-damaged skin) of fair-skinned older individuals (average age 65 yrs). It grows slowly over 5-20 years. The in-situ precursor lesion is usually large (1-3 cm or more in diameter), present for a minimum of 10-15 years, and demonstrates macular pigmentation ranging from dark brown to black, although hypopigmented (white) areas are common within lentigo maligna. Dermal invasion (progression to lentigo maligna melanoma) is characterized by the development of raised blue-black nodules within the in-situ lesion.
Acral lentiginous melanoma
- is the least common subtype (2-8% of melanoma cases in white persons). It accounts for 29-72% of melanoma cases in dark-skinned individuals (African American, Asian, and Hispanic persons) and because of delays in diagnosis, may be associated with a worse prognosis. Acral lentiginous melanoma occurs on the palms, on the soles, and beneath the nail plate (subungual variant). Subungual melanoma may manifest as diffuse nail discoloration or a longitudinal pigmented band within the nail plate. It must be differentiated from a benign junctional melanocytic nevus of the nail bed which has a similar appearance. Pigment spread to the proximal or lateral nail folds is termed the Hutchinson sign and is a hallmark for acral lentiginous melanoma.
Amelanotic melanoma (less than 5% of melanomas) is non-pigmented. It appears, clinically, pink or flesh-colored, often mimicking basal cell or squamous cell carcinoma or a ruptured hair follicle. It occurs most commonly in the setting of the nodular melanoma subtype or melanoma metastasis to the skin.
Primary risk factor for or clinical warning signs of melanoma include:
Changing mole (most important clinical warning sign)
Clinical atypical/dysplastic nevi (particulary more than 5-10)
Large number of common nevi (more than 100)
Large (giant) congenital nevi (more than 20 cm in diameter in an adult)
Personal history of melanoma or First-degree relative with melanoma
Sun sensitivity/history of excessive sun exposure
Prior nonmelanoma skin cancer (BCC or SCC)
Age older than 50 years
Surgery is the primary mode of therapy for localized cutaneous melanoma.
Malignant Melanoma; eMedicine Article, Jan 23, 2008; Susan M Swetter, MD
Current Treatments and Guidelines for Metastatic Melanoma; Medscape Article, 2007; Jedd D Wolchok, MD