Nevi and Melanoma in Children



Nevi and Melanoma in Children


Gina Prado





  • Pigmented lesions in childhood can pose diagnostic and therapeutic challenges for pediatric surgeons.


  • This chapter examines the common pigmented lesions encountered in childhood.


RELEVANT ANATOMY



  • 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





































Definition


Macule


Flat lesion with well-circumscribed skin color change <1 cm


Patch


Flat lesion >1 cm


Papule


Elevated solid skin lesion <1 cm


Plaque


Raised lesions >1 cm


Nodule


Lesion arising from the dermis or subcutaneous tissues


Nevus


Proliferation of cells within their own tissue of origin


Hyperkeratosis


Increased thickness of stratum corneum


Melanocytosis


Increased number of melanocytes


Acanthosis


Epidermal hyperplasia due to increased spinosum


Papillomatosis


Hyperplasia of dermal papillae



MELANOCYTIC NEVI



  • 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


Appearance


When to Biopsy


Acquired nevus


After age 6 mo; sun-exposed areas


Small (<5 mm)


Flat, symmetric, well-demarcated, dark pigmentation


Not indicated


Atypical nevus


Adolescence; sun-exposed areas, posterior trunk


5-15 mm


Irregular outline and uneven dark pigmentation, partially raised with a “fried-egg” appearance


Atypical change


Congenital nevus


At birth or within 6 mo of life; trunk


Variable size


Uniform and flat, may grow hair; various shades of blue, black, brown


Large lesions (>40 cm) should undergo biopsy


Halo nevus


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


Blue nevus


Childhood, dorsum of hands/feet


<5 mm


Smooth, blue-gray nodules


Not indicated


Cellular blue nevus


Any time


Scalp, sacrum, face


5-15 mm


Well-demarcated blue-gray nodule


Atypical change


Spitz nevus


Face, lower extremities


5-15 mm


Dome-shaped, smooth


Pink to red lesions


Atypical change


Becker nevus


Young male; upper torso and arm


Irregular hyperpigmented plaque


Brown pigmentation


Not indicated


Adapted from Holcomb GW, Murphy JD, Ostlie DJ, eds. Ashcraft’s Pediatric Surgery. 6th ed. New York, NY: Saunders; 2014.



May 5, 2019 | Posted by in PEDIATRICS | Comments Off on Nevi and Melanoma in Children
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