Melanoma
Background
What is the incidence of melanoma in the U.S.?
~70,000 cases/yr of melanoma in the U.S. (and rising)
What are some risk factors for developing melanoma?
UV RT, fair complexion, light hair/eyes, numerous benign nevi or larger atypical nevi (>5 mm, variable pigmentation, asymmetric, indistinct borders), personal Hx of melanoma (900 times), family Hx of melanoma, and polyvinyl chloride exposure
In terms of UV exposure, what is the most important risk factor associated with development of melanoma?
Intermittent intense exposure to UVA and UVB, such as Hx of blistering burns in childhood, is the most important risk factor for developing melanoma.
What are the gender differences in terms of body distribution of melanoma lesions?
Males: lesions predominantly on trunk (e.g., upper back)
Females: lesions predominantly on extremities
What % of melanomas derive from melanocytic nevi?
~15% of melanomas derive from melanocytic nevi.
What % of melanomas are derived from noncutaneous sites?
<10% of melanomas are from noncutaneous sites.
What are the common noncutaneous melanoma sites?
The GI, ocular, and gyn areas are the most common noncutaneous sites.
What % of melanoma pts have LN involvement at Dx, and how does this differ by T stage?
15% of pts have LN involvement at Dx, with 5% being T1 and 25% being ≥T2.
What % of melanoma pts present with DM at Dx?
5% of pts present with DM at Dx.
What proportion of DM pts present with DM from an unknown melanoma primary?
One third of DM pts or 1%–2% of all pts present with mets from an unknown primary.
What are the 5 subtypes of melanoma?
Superficial spreading, nodular, lentigo maligna, acral lentiginous, and desmoplastic variant
Which of the 5 melanoma subtypes is the most common?
Superficial spreading (70%) is the most common subtype → nodular (25%).
What are typical features of desmoplastic melanoma?
Features of the desmoplastic subtype include older pts (60–70 yo), more infiltrative, higher rate of perineural invasion, higher LF rates, and lower nodal met/DM rates.
Which melanoma subtype has the best prognosis?
Lentigo maligna melanoma has the best prognosis.
What is the LN+ rate and 5-yr OS for lentigo maligna melanoma?
For lentigo maligna melanoma, the LN + rate is only 10%, with 5-yr OS at 85% after WLE alone.
What subtype commonly presents in dark-skinned populations, and what body locations does it commonly affect?
Acral lentiginous, which commonly affects the palms/soles and subungual areas, is the most common melanoma subtype in dark-skinned populations.
Which subtype of melanoma is most common and has the worst prognosis?
Superficial spreading is the most common subtype. This subtype also has the worst prognosis.
What is the name for lentigo maligna involving only the epidermis (Clark level I)?
Hutchinson freckle is lentigo maligna of the −epidermis.
What are 3 commonly used immunohistochemical stains for melanoma?
S100, HNB-45, and Melan-A stains are commonly used for melanoma.
Workup/Staging
A pt presents with a pigmented lesion. What in the Hx can help to determine if this is a suspicious lesion?
Changes in ABCDE: Asymmetry, Borders, Color, Diameter (>6 mm), and Enlargement
What workup is necessary for tumors >1 mm thick?
For tumors >1 mm thick, provide a complete metastatic workup with CXR, LFTs, and CBC/CMP. CT C/A/P is needed for lesions >1 mm thick.
Per the latest NCCN guidelines, for what melanoma pts should imaging be performed?
Per the NCCN, imaging should be performed for −specific signs/Sx or stage ≥IIB (not recommended for stages IA, IB, and IIA).
What is the typical workup for small (<1-mm) melanoma lesions?
The workup is the same as for other skin cancers: H&P, CN exam (if H&N), regional LN exam, CT/MRI for extent/bone involvement, and tissue Bx.
What are some common DM sites for melanoma?
The skin, SQ tissues, distant LNs, lung, liver, −viscera, and brain are common melanoma DM sites.
What is the preferred method of tissue Dx for a suspected melanoma?
For suspected melanoma, full-thickness or excisional Bx (elliptical/punch) with a 1–3-mm margin is preferred for tissue Dx.
Why should wider margins on excisional Dx be avoided?
Avoid wide margins to permit accurate subsequent lymphatic mapping.
For what locations is full-thickness incisional or punch Bx adequate?
Full-thickness incisional and punch Bx are adequate for the palms/soles, digits, face, and ears or for very large lesions.
When is a shave Bx sufficient?
Shave Bx is sufficient when the index of suspicion for melanoma is low.
How do the Breslow thickness levels correspond to the latest AJCC T staging for melanoma?
The Breslow thickness levels are identical to and define the AJCC T staging of malignant melanoma:
T1: ≤1 mm
T1a: mitotic rate <1/mm2
T1b: mitotic rate ≥1/mm2
T2: 1.01–2 mm
T3: 2.01–4 mm
T4: >4 mm
T4a: no ulceration
T4b: ulceration
What is considered N1, N2, and N3 in melanoma staging?
All regional LN mets:
N1: 1+
N2: 2–3+
N3: ≥4+, or matted, or in-transit mets with mets to regional node(s)
For melanoma nodal groups, into what further categories are N1-N2 stages broken?
N1a: micromets
N1b: macromets
N2a: micromets
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