Nevi and Melanoma in Children
Premium Wordpress Themes by UFO Themes
Nevi and Melanoma in Children
The skin is the largest organ in the body and is composed of 3 layers: the epidermis, dermis, and subcutaneous fat. It serves many functions including thermoregulation, sensory perception, and protection microbial invasion.
The epidermis originates from ectodermal cells and consists of several layers: stratum basalis (inner layer), stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum (outer layer) (Figure 59.1
Cell types found in the epidermis includes keratinocytes, melanocytes, and Langerhans (dendritic) cells.
Keratinocytes are the stem cells that will repopulate the other layers over an individual’s lifetime.
They progress from the stratum basale to the stratum corneum.
Melanocytes are derived from neural crests cells and are found in the stratum basale.
Their primary function is to produce the pigment melanin for defense against UV injury.
Melanin accumulates in melanosomes, which are then phagocytosed by neighboring keratinocytes for melanin storage.1
Skin color results from the variable production and degradation of melanosomes and not on numbers of melanocytes.
Langerhans (dendritic) cells are bone marrow-derived, antigen-presenting cells that detect and present foreign antigen to T cells.
The dermis is of mesodermal origin and consists of consist of connective tissue, nerve endings, blood and lymphatic vessels, and adnexal structures (eg, hair shafts, sweat glands, and sebaceous glands).
It is divided into a superficial papillary layer and a deeper reticular layer.
Figure 59.1 Layer of the epidermis. (Reprinted with permission from McConnell TH, Hull KL. Human Form, Human Function. Philadelphia, PA: Lippincott Williams & Wilkins, a Wolters Kluwer Business; 2011.)
COMMON DERMATOLOGIC TERMS
Common terminologies to be familiar with are shown in Table 59.1
TABLE 59.1 Common Dermatologic Terminology
Flat lesion with well-circumscribed skin color change <1 cm
Flat lesion >1 cm
Elevated solid skin lesion <1 cm
Raised lesions >1 cm
Lesion arising from the dermis or subcutaneous tissues
Proliferation of cells within their own tissue of origin
Increased thickness of stratum corneum
Increased number of melanocytes
Epidermal hyperplasia due to increased spinosum
Hyperplasia of dermal papillae
Melanocytic nevi are divided into acquired nevi (those that appear after birth) and congenital nevi (those that are present at birth) (Figure 59.2
They are then further subclassified as junctional, compound, or dermal according to the location of the nevus cells in the skin.
Junctional nevi are at the junction of the epidermis/dermis.
Compound nevi involve both the epidermis and dermis.
Dermal nevi are confined to the dermis.
In childhood, >90% of nevi are junctional.2
Most nevi then become compound or dermal nevi as they migrate into the papillary dermis.
In general, the deeper the nests of nevus cells, the more raised and less pigmented the lesion (ie, dark flat lesions vs raised tan lesions).
The common variants of melanocytic nevi are shown in Table 59.2
TABLE 59.2 Common Melanocytic Nevi
Onset of Lesion
When to Biopsy
After age 6 mo; sun-exposed areas
Small (<5 mm)
Flat, symmetric, well-demarcated, dark pigmentation
Adolescence; sun-exposed areas, posterior trunk
Irregular outline and uneven dark pigmentation, partially raised with a “fried-egg” appearance
At birth or within 6 mo of life; trunk
Uniform and flat, may grow hair; various shades of blue, black, brown
Large lesions (>40 cm) should undergo biopsy
6-15 y; trunk, extremities
Central area of brown pigmentation with a rim of depigmentation, flat to slightly raised
Atypical change in center of lesion
Childhood, dorsum of hands/feet
Smooth, blue-gray nodules
Cellular blue nevus
Scalp, sacrum, face
Well-demarcated blue-gray nodule
Face, lower extremities
Pink to red lesions
Young male; upper torso and arm
Irregular hyperpigmented plaque
Adapted from Holcomb GW, Murphy JD, Ostlie DJ, eds. Ashcraft’s Pediatric Surgery. 6th ed. New York, NY: Saunders; 2014.
Acquired Melanocytic Nevi
Only gold members can continue reading. Log In
WordPress theme by UFO themes