Melanoma, Malignant

Key Features

Essentials of Diagnosis

• May be flat or raised with irregular borders

• Examination may show varying colors, including red, white, black, and blue

• Should be suspected in any pigmented skin lesion with recent change in appearance

• Less than 30% develop from existing moles

General Considerations

• Leading cause of death due to skin disease and fifth most common cancer

• Primary malignant melanomas may be classified into various clinicohistologic types

  • 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)

    • Diagnosis may be difficult or delayed because benign pigmented lesions in these areas occur commonly in more darkly pigmented persons; clinicians may hesitate to biopsy the palms and especially the soles and nail beds

    • Clinicians should give special attention to new or changing lesions in these areas

  • Malignant melanomas on mucous membranes

Demographics

• One in four cases of melanoma occur before the age of 40

• In 2021, approximately 106,110 new melanomas were diagnosed in the United States, approximately 60% in men

• Each year melanoma causes an estimated 7180 deaths (two-thirds in men)

• Lifetime risk is 2% in White and 0.1–0.5% in non-White individuals

Clinical Findings

Symptoms and Signs

• An irregular notched border where the pigment appears to be leaking into the normal surrounding skin

• Topography may be irregular, ie, partly raised and partly flat

• Color variegation, and colors such as pink, blue, gray, white, and black are indications for referral

• Bleeding and ulceration

• A mole that stands out from the patient's other moles (the "ugly duckling sign")

• A patient with a large number of moles is at increased risk for melanoma

• The history of a changing mole (evolution) is the single most important historical reason for close evaluation and possible referral

• Acral lentiginous melanomas: dark, sometimes irregularly shaped lesions on the palms and soles and new, often broad and solitary, darkly pigmented longitudinal streaks in the nails

Differential Diagnosis

• Acquired nevus (mole), eg, junctional nevus, compound nevus

• Seborrheic keratosis

• Lentigo, eg, solar lentigo

• Dermatofibroma

• Basal cell carcinoma (pigmented type)

• Congenital nevus

• Atypical (dysplastic) nevus

• Blue nevus

• Halo nevus

• Pyogenic granuloma

• Kaposi sarcoma

• Pregnancy-associated darkening of nevi

Diagnosis

• Skin biopsies

Treatment

Surgery

• Treatment starts with complete excision with a negative wide margin

  • After histologic diagnosis, reexcision is recommended with margins dictated by the thickness of the tumor

  • Recommended surgical margins are

    • 0.5–1 cm for melanoma in situ

    • 1 cm for lesions < 1 ...