Among all prognostic indications, depth of lesion is the most important.
Normal melanocytic nevi
common mole, derived from melanocytes occuring in clusters or nests)
Junctional nevus
– cells in Epidermal-Dermal Junction (EDJ).
Intradermal nevus
– cells in Dermis.
Compound nevus
– cells in EDJ and Dermis.
Precursor lesions
Acquired melanocytic nevi – risk of melanoma increases with increasing number of nevi.
Congenital melanocytic nevi
– risk of melanoma established in nevi > 6cm.
Atypical Moles (Dysplastic nevi)
- Hyperplastic and atypical melanocytes at DEJ and Dermis, appear to arise within preexisting compound or junctional nevi although may arise de novo.
Epidemiology
: lightly pigmented individuals, begin after puberty, autosomal dominant (9p) or sporadic, appear in 2% of general population, 25-40% of patients with sporadic melanoma, 100% of patients with familial melanoma.
Significance
: Malignant melanoma will arise in 0.7% of population without atypical nevi, 6% of population with sporadic atypical nevi, and 100% of population with familial atypical nevi (9p21, p16). Patients with familial disease must be followed every 3-6 months with excision of any changing lesions.
Malignant Melanoma
Melanoma accounts for 2% of all cancers (excluding non-melanoma cancers) and 1% of all cancer deaths.
Most frequent sites of location
:
White Patients:
Male – Back, anterior torso, upper extremity, head and neck.
Female – Back, lower leg, upper extremity, head and neck.
Black patients: (Acral-lentiginous melanoma) Soles, palms, and nails. Also mucous membranes.
Risk factors
: family history, multiple "atypical nevi", large congenital nevi, blond/red hair, marked freckling on upper back, 3+ blistering sunburns prior to age 20, 3+ summers of outdoors jobs as teenager, actinic keratoses.
Clinical diagnosis of melanoma
: see ABCs above.
Growth characteristics
:
Radial growth phase
– lateral extension to adjacent areas of skin usually seen in early stages of superficial spreading – lentigo maligna and acral-lentiginous melanomas; not present in nodular melanoma. Duration from weeks to years before vertical growth phase begins.
Vertical growth phase
– invasion into deeper portions of dermis including lymphatic and blood vessels. Seen in later stages of SSM, LMM, ALM; only stage present in NM. Risk of metastases increases greatly when tumor progresses to vertical growth phase.
Prognosis
: better in women; worse for lesions on trunk, in older patients, in larger and/or ulcerated lesions.
Prognosis is worst in "deeper" lesions
.
To measure depth of involvement (Breslow Level) use tumor thickness from top of tumor, not top of epidermis, to tumor bottom.
Staging
: the most important thing to know is that if the tumor progresses past Stage I (<0.76 mm) the percent survival drops significantly.
Differential Diagnosis
: Blue nevus, Seborrheic keratoses, Melanocytic nevi, Spindle and epithelioid cell nevus (Spitz nevus), Pigmented basal cell carcinoma, Pyogenic granuloma.
Treatment
:
Surgical
Chemotherapy – not very effective.
Radiation – melanoma is radio-resistant.
Immunotherapy – interferons, etc. Modest results with a lot of side effects.