CMN and expanders

1. CONGENITAL MELANOCYTIC NEVI
+ TISSUE EXPANDER
Dr Mujtuba Pervez Khan
Resident Plastic Surgery
DUHS/CHK

2. • Rare
• Mostly sporadic
• Familial association is occasionally observed.
• Form between weeks 9 and 20 week of gestation
• Giant CMN 1 in 20,000 live births

3. EMBRYOLOGY
• 8 -10 wks of gestation, melanoblasts migrate
from the neural crest to skin, leptomeninges,
eyes, and ears
• Differentiate into dendritic melanocytes.
• Abnormalities in neuroectodermal
development and arrested migration or
diffrentiation of melanoblasts result in the
formation of a CMN.

4. TYPES OF NEVI:
• SMALL NEVI : <1.5 cm
• MEDIUM SIZED NEVI : 1.5 and 19.9 cm.
• GIANT NEVI : >20 cm
• In an infant, 9 cm scalp and 6 cm over the trunk

6. CHARACTERISTICS
• Initially hairless, pale brown, flat
• Hyperpigmentation, hairs may develop,
elevated
• Surface can be wrinkly, pebbly or
cerebriform appearance.
• May be associated with multiple
smaller satellite lesions dispersed over
the trunk, extremities or head and
neck
• Satellite lesions in 80% of giant CMN.

7. CHARACTERISTICS
• Giant CMN may be associated with
Spina bifida
Scoliosis
Elephanitiasis
Clubfoot
Cranial osseous hypertrophy

8. • Common sites: posterior trunk,
extremities, head and neck
• Giant nevi anatomic patterns, bathing
trunk and glove- stocking
distributions.
• kissing nevus

9. HISTOLOGIC FEATURES OF CMN
• Nevus cells within the middle to deep reticular dermis and
subcutaneous tissue or deeper structures
• Nevus cells extending between collagen bundles in the reticular
dermis (Indian files) and around sebaceous glands, sweat glands
and hair follicles
• Infiltration of arrector pili muscle
• Perifollicular and perivascular distribution of nevus cells
resembling an inflammatory reaction.

10. DIFFERENTIAL DIAGNOSIS
• Café au lait spots
• Nevus sebaceous
• Mongolian spots
• Epidermal nevus

11. Malignant Transformation:
• Melanoma in small CMN 0% - 5%
• Melanoma in Giant CMN 0% - 42%
• 70% of melanomas in giant CMN occur by age 13, 50% arising in the first 3
years of life, 10% in childhood and 10% by puberty.
• Risk factors: 1) size (diameter> 20 cm) 2) young age (3 to 5 years) 3)
multiple lesions (three or more)
• Melanoma in Giant CMN deep to the dermal-epidermal junction or
extracutaneously e.g the central nervous system or retroperitoneum
• In small CMN: epidermis.
• Ulceration, bleeding, uneven pigmentation, change in shape, focal growth
or pain -> Biopsy

12. Neuro-cutaneous Melanosis
• Melanocytes present in the leptomeninges
• Dysregulation in proliferation and migration of melanoblasts in the
CNS
• Morbidity and mortality from seizures, hydrocephalus, cranial nerve
palsies, developmental delay, and other signs of CNS irritation.
• Risk factors: 1. CMN in the midline of the trunk or skull 2. multiple
satellite nevi (>20)
• MRI at 4 and 6 months of age prior to normal myelination of the
brain, which will obscure visualization of deposits of melanin.

13. history
 Duration
 Color, flat, hairy
 With time became more pigmented, elevated and increased hair growth.
 other lesion on body
 history of fits or any other neurological symptoms
 recent change in behaviour of lesion, any pain, irregularity of borders, ulceration,
bleeding
 Systemic review on history
 Social behaviour
 PAST MEDICAL AND SURGICAL HISTORY
 FAMILY HISTORY
SOCIO ECONOMIC HISTORY

14. examination
Site
extent
Size
Shape
Hair growth, pigment, colour
 edges
 Surface: leathery?
Direction of hair
 Satellite lesions
 Eye movement and vision
 Other lesion on rest of the body
 SYSTEMIC EXAMINATION

15. MANAGEMENT
Non Excisional
Methods
Chemical
peels
lasers
dermabrasion
curettage
Excisional
Methods
primary
excision and
closure
serial excision
tissue
expansion
skin grafting
skin
substitutes

16. Anatomic sites
• Scalp = expander
• Frontotemporal region = expander
• Forehead = expander/ FTG
• Nose = Expander forehead flap
• Cheek = expanded cervical/post auricular flap
• Eyelid = FTG
• Ears = FTG/ post auricular flap, helical rim advancement

17. TISSUE EXPANSION:
• Mechanical Creep (cellular stretch) 70%
• Biological Creep (cellular proliferation) 30%
• Stress relaxation
• Mechanism of tissue creep:
1. Disruption of elastin fibres
2. Realignment of collagen
3. Fluid displacement
4. Migration of local tissue

18. ADV:
1. Replacement of tissue of similar color and texture
2. Sensate skin coverage with skin appendages
3. Limited donor site deformity
• Expanded flap has superior vascularity
• Epidermal thickening, dermal thinning

19. • Capsule forms around the expanded
1. Inner Zone: Fibrin layer with macrophages
2. Central Zone: Fibroblast and myofibroblasts between collagen
bundles
3. Transitional Zone: Losse collagen fibres, few blood vessels
4. Outer Zone: Loose collagen fibres, established vascular layer

20. • Expander Types
1. Shape
2. Sizes/Volume
3. Port location

21. Planning
• Incision at the border of the lesion
• 10 – 20% expansion at the time of placement
• Use larger ports for easier palpability and to avoid flipping of port
• Pocket incision is closed in a watertight fashion
• Expansion begins after 7-10 days, depending upon the condition of
the flaps
• Should be filled till the skin is tense, not painful or cause skin
compromise
• Weekly expansion

22. Planning

23. Planning
• Expanded flaps can be advanced, transposed or rotated.
• In face and trunk, expander is placed subcutaneously
• In forehead and scalp, it is placed in subfascial plane
• When fully expanded, wait for 3-4 weeks before the 2nd stage

24. Contraindications
• In the vicinity of an immature scar
• In presence of infection
• In irradiated skin
• Under the skin graft

25. Complications

26. Scalp
• 2nd most common site
• CMN, scar alopecia, craniofacial abnormalities
• Temporary cranial moulding occurs, correct within 3-4 months
• Serial expansion to distribute expansile forces evenly over the hair
follicles
• Subgaleal plane
• Port placement in pre auricular region produces least migration
• 50% scalp can be covered without significant hair thinning

28. Forehead
• Less than 2/3rd involved = expander
• Entire forehead = FTG
• Complications: Brow asymmetry, brow ptosis, altered hair direction,
hairline asymmetry
• Principles:
1. Mid forehead lesion = Bilateral expansion
2. Hemi forehead lesion = Serial expansion
3. Supra orbital, Temporal nevi = Expansion and transposition from
medial normal skin
4. Mild temporal nevi = expanded parietal skin
5. Brow elevation = interposing non hair bearing forehead skin

29. Face and neck
• Hide scars in natural creases
• Tension in middle and lower face can cause Lower lip droop, oral
incompetence, asymmetric smile. Specially for expanded cervical
flaps
• Expanded lateral cheek, neck, post auricular region
• Expanded FTGs

31. Abdomen
• Easily expanded
• Expanded ftgs
• Expanded flaps for anterior thigh defects
• Expanded free TRAM flap
• Upper abdomen and anterior trunk -> breast distortion

32. Back
• For CMN of back and buttock
• Aesthetic and functional position of scar

33. Extremities
• Unfavorable site
• Proximal non circumferential defects = expanded flaps from the back
or shoulder
• Proximal circumferential = expanded free TRAM flap
• Distal circumferential mid – lower forearm = expansion of flank
• Fingers, webs and hands = expanded ftg from abdomen/groin
• Lower limb = lacks flexibility, expanded free flaps, expanded local
flaps serial excision, FTGs

34. Breast
• Post mastectomy reconstruction
• Poland syndrome, unilateral breast hypoplasia
• Expanders, expander implants

35. Thanks.