|Congenital Melanocytic Nevus
Defined as benign nevomelanocytic proliferations present at birth.
Rarely, melanocytic nevi with features indistinguishable clinically and histologically from typical congenital melanocytic nevi appear in children between 1 month and 2 years of age. This subset is termed nevus tardive
Large >20cm >2%BSA or 1%SA of Head
Generally, congenital melanocytic nevi are round to oval in shape and have a regular, smooth, and well-demarcated border.
After the first 6 months, the lesions grow proportionally to the particular area of the body involved
Clinical appearance may change with age.
In neonates, the moles may be light in color and relatively hairless, with a flat or raised surface. As the child grows, the nevi may become progressively darker, with a uniform brown to dark brown or black color and may acquire long, coarse, darkly pigmented hairs.
May exhibit a papular, rugose, pebbly, verrucous, or even cerebriform surfaces
Satellite smaller melanocytic nevi may also be present,
“Kissing nevus,” or divided nevus of the eyelid, is an interesting clinical variant of congenital melanocytic nevi. It occurs on adjacent parts of the upper and lower eyelids and appears contiguous, as a single lesion, when the eyelids are closed. This finding implies that congenital melanocytic nevi develop between the 9th and 20th week of gestation, when the eyelids are fused
nevomelanocytes splaying or extending between the collagen bundles of the reticular dermis as single cells, “Indian” files, or cords of cells
nevus cells in lower 2/3rd dermis
extension of nevomelanocytes around and within hair follicles, sebaceous glands, eccrine apparatus, vessel walls, and nerves
perivascular and perifollicular distribution of nevomelanocytes simulating an inflammatory reaction such as figurate erythema
arrector pili that may be enlarged, distorted, and infiltrated by nevomelanocytes.
Atypical features of congenital nevi include
dysplasia of intraepidermal nevomelanocytes
pagetoid spread of nevomelanocytes - pagetoid intraepidermal growth pattern in benign melanocytic nevi is confined to the area of nested intraepidermal proliferation, in contrast to melanoma in which the pagetoid growth is observed as lateral spread beyond the nested proliferation
proliferative dermal nodules.
Distinctive “Indian file” array of nevomelanocytes.
During the first 6 months of life, some nevi can appear to ‘‘grow’’ significantly as tardive pigment becomes more visible.
Some satellite nevi may become visible for the first time over the first 2 to 3 years (tardive CM)
scoliosis, spina bifida, clubfoot, cranial bone hypertrophy
First described by Rokitansky
presence of giant (2/3rd) or multiple(1/3rd) melanocytic nevi associated with benign or malignant melanotic tumors of the central nervous system.
posterior axial location, especially when associated with "satellite" melanocytic nevi at greatest risk
Called leptomeningeal melanocytosis with CMS melanoma
Leptomeningeal melanoma present in upto 62% of the cases, but even in the absence of melanoma, symptomatic neurocutaneous melanosis has an extremely poor prognosis.
Patients with large or multiple congenital melanocytic nevi in axial locations (head, neck, or posterior midline) or multiple satellite lesions seem to have an increased risk of leptomeningeal melanocytosis.
Most case are sporadic, and no gender or racial predilection is evident.
Melanocytes of both skin and leptomeninges are thought to be derived from multiple potential precursor cells of the neural crest, NCM is postulated to represent a congenital error in embryonic neuroectoderm morphogenesis.
CSF shows increased protein, decreased sugar, and a normal cell count.. May show melanin-filled cells
Criteria for the diagnosis of neurocutaneous melanosis:
The presence of large or multiple congenital melanocytic nevi (one of which is at least 20 cm in diameter) with benign (melanosis) or malignant (melanoma) central nervous system (CNS) tumors.
The absence of malignant melanoma in any organ (including skin) other than the CNS.
accumulation of melanotic cells in the arachnoid and pia mater
Parenchymal melanin deposits probably represent melanocytes in the perivascular spaces.
Hydrocephalus – usually secondary to meningeal thickening,
Cranial nerve palsies
Spinal cord compression
MRI – T1 shortening characteristic
death occurred in more than half the patients within 3 years of the onset of neurological symptoms, most <10 years old
2 main concerns
Risk of melanoma
Stigma of visible lesion and how it will affect psychosocial development
Risk of melanoma
In general, risk is related to nevomelanocytic load
In several case series, no melanoma noted in small and intermediate lesions
Approximately 50% of the malignancies that develop in large CMN do so in the first 3 years of life, and 70% by puberty (<10yr old)
Giant melanoma – 2 prospective studies
Ruiz-Maldonado (1992): Three of 80 patients (3.8%) developed cutaneous melanoma during an average follow-up period of 4.7 years
Marghoob (1996): Ninety-two patients were followed up prospectively for an average of 5.4 years. Melanoma developed in 3 patients (3.3%) in extracutaneous sites.
Watt (PRS 2004) – review of 8 studies. Observed incidence of melanoma was 2600 times higher than would be expected.
majority of melanomas that arise in association with large or giant congenital melanocytic nevi originate in the dermis. They are usually composed of epithelioid cells, spindle cells, or small round cells.
Melanomas arising in small congenital melanocytic nevi usually originate in the epidermis
To date, no case of melanoma has been reported arising in a satellite nevus
Rationale for early treatment
greatest risk of melanoma during early years
elasticity and healing capacity of the skin in the early years
more tolerant to surgery /tissue expansion
Q-switched ruby laser
staged excision and reconstruction
Dermabrasion and curettage
remove the more concentrated population of nevus cells near the lesion’s surface.
Theory is that the nevus cell migrate deeper with age
can be effective in reducing the overall nevus ‘‘cell load’’ but cannot fully remove the nevus, because of the well-known depth of nevus cells in CMN
may result in significant lightening of the color of the lesion, it is quite common to see later ‘‘bleed-through’’ of the deeper nevus, with gradual darkening and reappearance of the lesion.
lightening of pigmented giant congenital nevi using these techniques may make it more difficult to monitor the resultant lesion for signs of malignant transformation, because alteration in pigmentation of the lesion can no longer be followed reliably.
no longitudinal studies documenting decreased rates of malignant transformation after laser or dermabrasion treatment.
there is no evidence in the existing literature that the excision of large congenital melanocytic nevi decreases the prevalence of melanoma.
undertaken if lesion can be removed in 3-4 excisions. Otherwise tissue expand.
SSG or full thickness grafts(preferred)
FTSG donor sites – postauricular, supraclavicular, buttock, groin, medial arm, abdomen
May be expanded to increase donor area
Use of Integra at recipient site may improve scar
Tissue expansion (Bruce Baeur)
Advantage - large flaps of color-, thickness-, and texture-matched skin while simultaneously minimizing donor-site defects.
optimized to ensure that the landmarks of the forehead aesthetic unit will be disturbed as little as possible.
Particular emphasis is placed on brow symmetry, temporal hairline position and hair direction, and scar orientation.
Treatment starts as early as 6 months, with some cranial molding expected by the time the expanders are removed
No instance of long-term cranial deformity has been noted (remodeling usually occurs over 3 to 4 months).
Rectangular expanders with remote ports, placed subgaleal (250-500ml size)
Usually 2 expanders used
Expanded weekly, 2nd stage in 10 weeks