Cutaneous Melanoma

93


Cutaneous Melanoma




A malignant tumor of melanocytes, most commonly arising from cutaneous melanocytes; can also develop from melanocytes residing elsewhere – e.g. in the uveal tract, retinal pigment epithelium, gastrointestinal mucosa, or leptomeninges.


Some cutaneous melanomas (CMs) arise de novo, whereas others arise within precursor lesions (e.g. melanocytic nevi; see Chapter 92).


Tremendous advances have been made in understanding the molecular pathways and mutations from which many CMs originate, resulting in identification of genetic markers, tools for aiding in the histologic diagnosis, and targeted treatments for CM (Figs. 93.1 and 93.2; see Table 93.11).





Epidemiology



There has been a marked increase in the incidence of CM during the past 40–50 years, with a modest increase in mortality, especially among older males (Figs. 93.3 and 93.4).




Death occurs at a younger age than for most other cancers.


Risk factors are divided into three major groups: genetic, environmental, and phenotypic (Table 93.1).



Familial atypical multiple mole melanoma (FAMMM) syndrome is defined as families with atypical (dysplastic) nevi and ≥2 blood relatives with melanoma; carries up to an 85% risk of developing CM by age 50 years in affected family members; some families with CDKN2A mutations have both melanoma and pancreatic cancer.


Primary prevention: sun protective measures and avoidance of tanning beds.


Secondary prevention: early detection.



Clinical



The clinical presentation of CM varies greatly; although the ABCDE‘s (Asymmetry, Border irregularity, Color variegation, Diameter >6 mm, Evolution) are often used in public awareness campaigns to help promote the clinical recognition of CM, they have their shortcomings; to rectify this, the EFG rule (Elevated, Firm, Growing) has been added for nodular and amelanotic CMs.


As banal nevi age, they also become more elevated, but in contrast to nodular CMs, they are soft to palpation.


There are four major subtypes of primary invasive CM, based on clinicopathologic features:


Superficial spreading melanoma (SSM; ~60% of melanomas) (Fig. 93.5).



Nodular melanoma (NM; ~20%) (Fig. 93.6).



Lentigo maligna melanoma (LMM; ~9%) (Fig. 93.7).



Acral lentiginous melanoma (ALM; ~4%) (Fig. 93.8).



In cutaneous melanoma in situ (MIS), the malignancy is confined to the epidermis and/or the hair follicle epithelium (Fig. 93.9); all types of CM (except for NM) can have an in situ phase; lentigo maligna is a type of MIS that arises within chronically sun-damaged skin and can remain in situ for years to decades.



Less common variants of CM:


Amelanotic melanoma: color ranges from pink to red and any type of CM may be amelanotic (Fig. 93.10); children can develop amelanotic nodular CM, and the lesion may resemble a persistent arthropod bite or pyogenic granuloma.


Apr 22, 2016 | Posted by in Dermatology | Comments Off on Cutaneous Melanoma

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