Melanoma
last authored: Sept 2009, David LaPierre
last reviewed:
Introduction
Half of all melanomas arise in clinically normal skin, and 1/3 originate from pre-existing nevi.
Lifetime risk of a mole becoming melanoma is perhaps 1:3000 for women and 1:10,000 for men (Tsao et al, 2002).
The Case of...
a simple case introducing clincial presentation and calling for a differential diagnosis to get students thinking.
Causes and Risk Factors
UV-B exposure, pre-existing nevus, congenital nevus
- family history of melanoma
- personal history of melanoma
- fair skin type (Fitzpatrick)
- red hair
- Xeroderma pigmentosum
Pathophysiology
Types of melanoma include:
- superficial spreading
- lentigo maligna (Hutchinson's)
- acral lentiginous
- nodular
Superficial Spreading
Most common ages 30-50 on the trunk in men and women and on the legs in women.
Lesions are flat or slightly elevated; brown is most common, but may also have black, blue, pink, or white discoloration. Generally greater than 6 mm in diameter with irregular, assymetric borders.
Histology shows scattered atypical melanocytes within the epidermis.
Lentigo Maligna
Lentigo maligna is slow-growing. They are typically located on sun-exposed areas (head, neck, and arms) of fair-skinned older individuals (average age 65 y).
Lesions are often present for 5-20 years, with an initial central lesion that becomes surrounded by areas of dermal invasion.
Acral Lentiginous
nodular
Occurs in 15-30% of patients, most commonly on the legs and trunk.
Rapid growth occurs over weeks to months; this subtype is responsible for most thick melanomas.
It manifests as a dark brown-to-black papule or dome-shaped nodule, though may also lack pigmentation.
ABCDE warning signs are often absent, leading to presentation with elevation, ulceration, or bleeding.
Histologically, it lacks a radial growth phase.
Signs and Symptoms
- history
- physical exam
History
Patients should be aware of their skin and of any changes they notice. Symptoms can include:
- bleeding
- itching
- ulceration
- pain
Family history is also important.
Physical Exam
Examination of a suspicious lesion includes the ABCDEs
- Asymmetry: Half the lesion does not match the other half.
- Border: edges are ragged, notched, or blurred.
- Color: not uniform, with different colours including tan, brown, black, white, reddish, or blue
- Diameter: larger than 6 mm (a pencil eraser)
- Evolution: Changes over time; critical for nodular or amelanotic (nonpigmented) melanoma
Diagnosis
If lesion small or in inconsequential area: excisional biopsy
If lesion large or in esthetically sensitive area (eyelid): punch biopsy
Biopsy confirms diagnosis but more importantly assesses depth (1° determinant of prognosis)
Differential Diagnosis
Treatments
Surgery
When determining surgical margins:
- in situ: 0.5 cm
- <1 mm: 1 cm
- 1.1-2.0 mm: 1-2 cm
- 2-4 mm: 2 cm
- >4mm: 2-3 cm
Can dissect sentinel nodes with dye tracing and scintillography; good for prognosis; not clear data on benefit for survival.
Lesions ≤1 mm deep need wide local excision (WLE) alone. Deeper lesions which are clinically node-negative need WLE + sentinel LN biopsy, proceeding to formal LN
Dissection ± parotidectomy only if SLN(s) are positive histologically.
Melanoma which is node-positive at presentation should be offered WLE with lymphadenectomy, but this is primarily for locoregional control and has limited bearing on overall survival.
Adjuvant treatment with α-interferon: survival benefit equivocal.
Consequences and Course
Prognosis is most determined by Bredslow thickness
Resources and References
Topic Development
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