The document discusses various types of melanocytic lesions of the skin except melanoma. It describes: 1. Benign pigmented lesions arising from epidermal melanocytes such as freckles, solar lentigines, and melanotic macules. 2. Lesions arising from dermal melanocytes including Mongolian spots, nevi of Ota and Ito, and blue nevi. 3. Benign tumors arising from nevus cells including congenital and acquired nevi, and special variants like Spitz nevi, balloon cell nevi, and dysplastic nevi.

1. Melanocytic Lesions
Of Skin
Except Melanoma
 Dr Nidhi Rai

2. • Melanocytic proliferations are composed of one or
more of three related types of cells:
• Melanocytes,
• Nevus cells,
• Melanoma cells
Each of which may be located in the epidermis or in the
dermis

3. NEVUS CELL MELANOCYTE MELANOMA
CELL
Type Round or spindle
shaped
Dendritic Round or spindle
shaped
Grouping Clusters Solitary Clusters & sheets
Nuclei Vesicular with
nucleolus
Small & regular
dark staining
shrunken
Large & atypical
Mitosis Rare Rare Common &
atypical

4.  Melanocytes are solitary Dendritic cells that generally are separated from
one another by other cells (keratinocytes or fibroblasts).

6. BENIGN PIGMENTED LESIONS
Epidermal
melanocytes
Dermal
melanocytes
Benign
tumor of
nevus cells

7. FROM EPIDERMAL MELANOCYTES
Ephelides
Solar lentigenes ( actinic/senile lentigo)
Lentigo Simplex
Melanotic macule of Albright’s syndrome
Becker’s melanosis

8. Freckle (EPHELIDES)
• Usually appear in first 3 yrs of life.
• Common – Red hairs / blue eyes.
• Due to increased sun induced
melanogenesis.
• 1-3 mm red brown macule over sun
exposed skin.
• Further exposure to sun deepens the
pigmentation.

9. Microscopy :
• Hyperpigmentation of the
basal cell layer
• No elongation of the rete
ridges
• No obvious increase in the
concentration of melanocytes.
• Represent a hyperplastic and
hyperactive response of
melanocytes to UV light.

10. Melanotic Macule Of Albright’s
Syndrome
• Albright’s syndrome –
 Unilateral polyostotic fibrous
dysplasia.
 Precocious puberty in females.
 Melanotic patches.
(Large and few in number ,
located on only one side of the
midline, and have a jagged,
irregular border.)

11. Microscopy:
• Hyperpigmentation of the basal layer and both the number and
size of the melanocytes are normal .
D/D:
• Cafe-au-lait patches of neurofibromatosis ( Smooth border of
lesions)

12. Lentigines
• Latin word – Lenz , meaning lens or lentil, clinically referring
to the appearance of small ovoid or lens shaped pigmented
spot.
• Macular hyperpigmentations in which the number of epidermal
melanocytes is increased & no nests of melanocytes as in nevi.
• Lentiginous proliferation – basal proliferation of melanocytes
as single cells with elongation of rete ridges.

13. Solar Lentigo (Actinic Lentigo)
• Multiple scattered small brown
macules on sun-damaged areas
• Male
• Increase in number with age (Senile
lentigines).
• Microscopy:
 Elongated & clubbed/ tortuous rete
ridges c/o pigmented basaloid cells.

14.  Slight to moderate prominence of
melanocytes along basal layer
without contiguous proliferation.
 Upper dermis- Elastosis &
scattered melanophages.
Differential diagnosis –
• Lentigo simplex
• Lentigo maligna

15. Lentigo Simplex
• Early onset (Childhood).
• Unrelated to sun exposure.
• Few scattered small, symmetric and
well circumscribed evenly pigmented
macules.
• Microscopy:
• Increased number of melanocytes in
epidermal basal layer and focally lie in
contiguity.
• Elongated rete ridges-heavily
pigmented & have branching
downgrowths -dirty feet appearance.
• N0 nests
D/D- Junctional nevus

16. Becker’s Melanosis
• Malformation involving the epidermis ,
pilosebaceous units & erector pilli muscle.
• Increased androgen receptors & heightened
sensitivity to androgen – occurs after
puberty.
• Large U/L poorly demarcated patch with
hyperpigmentation & hypertrichosis.
• Shoulder , back or chest of a adult male

17. Microscopy :
• Acanthosis, hyperkeratosis
• Regular elongation of rete
ridges
• Hyperpigmentation of basal
layer, number of melanocytes
increased
• Increased smooth muscle
fibers in dermis

18. Clinical Basal
Layer
Melano-
cytes
Features
Ephelids Sun exposed
skin
Decreases with
age
Inc. Melanin Normal
Melanotic
Macule Albrights syn. Inc. Melanin Normal
Beckers
Melanosis
U/l
hypertrichosis Inc. Melanin Increased
Elongated rete,
smooth muscle
fibres in dermis
Solar
Lentigo
Sun exposed
skin
Increases with
age
Inc. Melanin Increased
No contiguity
Elongated rete,
solar elastosis
Lentigo
Simplex
Not related to
sun exposure
Inc. Melanin Increased
Focal contiguity
Elongated rete
(Dirty feet
appearance)

19. From Dermal Melanocytes
Persistent
Mongolian
Spot
Nevi
of
Ota & Ito
Blue nevus-
common ,
cellular ,
combined

20. • Melanocytes appear in dermis- 10 th week of gestation
• Except in dermis of scalp, extensor aspect of extremeties and
sacral region
• Blue colour- Tyndall Phenomenon- decreased reflectance in
longer wavelength region( red, yellow ,orange)
Migrate into epidermis Undergo cell death

21. Mongolian Spot
• Appears at birth
• Disappears at 3-4years.
• Sacrococcygeal region.
• Uniformly blue discoloration

22. No pigmentary changes in epidermis
No melanophages
Elongated,slender,slightly wavy dentritic
cells containing melanin granules ,between
the collagen bundles in the lower dermis

23. Nevus Of Ota
• Oculodermal melanosis.
• Present at birth.
• Ill defined brown to slate blue U/L lesion
in distribution of ophthalmic &
maxillary division of trigeminal nerves.
• Malignant changes – rare
• Associated with persistent mangolian
spots.

24. Nevus Of Ito
• U/L slate blue mottled , macular
pigmentation.
• Regions Supplied by posterior
supraclavicular & lateral brachial
cutaneous nerves (supraclavicular,
scapular & deltoid regions)

25. Microscopy:
Hyperpigmentation of epidermis Bipolar melanocytes dispersed singly in
superficial dermis

26. Blue Nevus
• Benign, localized pigmented lesions.
• On skin 3 types –
 Common blue nevus
 Cellular blue nevus
 Combined nevus
• Childhood – extremities & scalp
• Histologically common feature - Presence of dendritic
melanocytes in reticular dermis associated with variably
stromal fibrotic response.

27. Common Blue Nevus
• (<10 mm) bluish-grey well
circumscribed dome shaped
papule.
• Near dorsa of the hands & feet ,
scalp.
• Microscopy:
 Normal epidermis.
 Pigmented spindle and dendritic
melanocytes in a focal area of the
reticular dermis, associated with
thickened collagen bundles.

28.  typically larger and their
density is much greater
 Cells have plenty of
melanin.
 Melanophages are seen, but
not numerous or dense.
 Melanocytes - positive for
S-100, HMB-45 & Melan-
A.
• D/D –
Dermatofibroma
( If minimally pigmented)

29. Cellular Blue Nevus
• blue nodule,1 to 3 cm in diameter.
• buttocks or in the sacrococcygeal
region.
• Microscopy:
• bulky, heavily pigmented cellular
tumor .
• spanning the reticular dermis.
• Extend into the subcutis forming
a bulbous expansion
( Dumb Bell Pattern).

30. • comprising of deeply pigmented dendritic melanocytes +
cellular islands large spindle shaped or epitheloid cells with
ovoid nuclei and abundant pale cytoplasm often containing
little or no melanin.
• Melanophages often seen.
• Four histological subtypes:
1. Mixed biphasic
2. Alveolar
3. Fascicular or neuronevoid (monophasic spindle-cell type)
4. Atypical varieties

31. Spindle cells lie in contiguity with one
another, unlike the cells of common
blue nevi, most of which are separated
from one another by collagen bundles
Mixed biphasic pattern , with ovoid
islands of polygonal cells with somewhat
clear cytoplasm alternating with spindle
cells, the latter often pigmented.

32. SPECTRUM OF HP FEATURES OF INTRADERMAL
MELANOCYTIC PROLIFERATIONS
MELANO-
CYTOSES
COMMON
BLUE NEVUS
CELLULAR BLUE
NEVUS
COMBINED
NEVUS
Paucicellular,
Interstitial
proliferation of
bland Dendritic
melanocytes
sclerotic stroma
+ heavily
pigmented
lesion larger, deeper
+Oval melanocytes
with abundant
cytoplasm with little
or no melanin
MF+
blue nevus with
an overlying
melanocytic
nevus or to
other
combinations of
benign nevi

33. Arising From Nevus Cell - Melanocytic
Nevus
CONGENITAL ACQUIRED
• Junctional
• Compound
• Intradermal
SPECIAL
VARIANTS
• Spitz
• Dysplastic
• Halo
• Deep
Penetrating
• Recurrent
• Pigmented
Spindle Cell
Tumor Of Reed
• Balloon Cell

34. • Benign non neoplastic proliferation of melanocytes
• Pigmented or nonpigmented lesions ,< 5 mm in diameter.
• Adolescence or early adulthood, rarely at birth.
• Cells arranged in cohesive nests with relative uniformity of the
nevus cells and fairly regular spacing of the nests.
• Nests located at the tips of the rete ridges (for junctional and
compound nevi)

35. CONGENITAL NEVI
• Found in 1% of newborn.
• Usually solitary – trunk , lower
extremities and scalp
• larger than acquired nevi
measuring >1.5 cms.
• Giant congenital nevi,(garment
nevi)- > 20 cms
• Giant congenital melanocytic nevi
– increase risk of the development
of melanoma.

36. • Microscopy:
 May be junctional, compound
or intradermal
 Presence of melanocytes
around and with in the
adenxae ,nerves , vessel wall.
 Nevus cells extend between
collagen fibers singly or in a
Indian file pattern-
characteristic feature.
nevus is very broad and deep-
epidermis-dermis-fat
spindle shaped heavily pigmented

37. ACQUIRED NEVI
• More prevalent in boys, more in fair skin and blond or red
hair.
• Undergo progressive maturation with increasing age of the
lesion.
• The lesion become stable after growing to some size and may
even involute. With advancing age there is progressive
decrease in the number of nevi
Histopathological types Clinical types
Junctional Flat macules
Compound Pappilomatous
Intradermal Dome shaped,
pedunculated lesion

38. Junctional Nevus
• Well circumscribed brown
to black macules, any where
• childhood or early adolescence
• Microscopy:
 Presence of well circumscribed
nests of cohesive melanocytes
either within lower epidermis or
bulging into dermis.(theque)
 Originating from tips and sides
of rete ridges.

39. • Variable lentiginous melanocytic hyperplasia.
• No continuous proliferation of melanocytes in the
suprapapillary regions of the epidermis between the rete
ridges.
• Melanophages in dermis
• D/D –
1. Lentigo simplex - no theques
2. Junctional lentiginous melanocytic nevus- not circumscribed

40. Compound Nevus
• Elevated pigmented papule.
• Microscopy:
 Junctional melanocytic theques
+ dermal population of
melanocytes (Nevus cell nests
are present in the epidermis as
well as appearing to ‘drop off’
into the dermis).
 Periadenexal & adventitial
dermis spared Compound nevus: both junctional and
dermal nests of nevus cells

41. • The nevus cells change their morphology as they go deeper
into the dermis. Three morphologic subtypes of nevus cells
are recognized, from superficial to deep:
TYPE LOCATION SHAPE MELANIN
A
(epithelioid)
upper dermis Round to polygonal
with abundant
cytoplasm
variable
B
(lymphocytoid)
mid-dermis same but smaller
than type A
less than A
C lower dermis elongated spindle
shaped ( fibroblast)
rarely contain

42. INTRADERMAL NEVUS
• Adults, dome shaped lesions
flesh coloured
• Microscopy:
 Upper dermis -
 nests and cords of nevus cells
concentrated around
pilosebaceous units.
 Multinucleated nevus cells -
small nuclei in a rosette-like
arrangement or close together
in the center of the cell.

43.  Lower dermis –
 Less cellular c/o spindly cells,
similar to that of the fibers in a
neurofibroma(neurotized nevus).
 In other areas, the nevus cells
lie within concentrically
arranged structure , resemble
Meissner's tactile bodies.
 Clefts - between some nests of
nevus cells and the surrounding
epidermis as well as stroma,
simulates a lymphatic space and
mimics lymphatic invasion
cell nests having a neuroid
differentiation

44. SPECIAL VARIANTS

45. BALLOON CELL NEVUS
• Clinically indistinguishable from
melanocytic nevi
• Microscopy-
 Epidermis - Balloon cells seen
singly or in groups or absent .
 Dermis - arranged in lobules of
varying size admixed with
ordinary nevus cells.
 Large cells , small round centrally
placed nucleus with empty , finely
granular or vacuolated cytoplasm

46.  Large vacuoles – Enlargement and coalescence of
degenerating melanosomes.
 Stains for lipid, glycogen and acid or neutral
mucopolysaccharide – negative.
D/D –
 Large adipocyte in intradermal nevi – Flattened nucleus at
periphery.
 Clear cell hidrenoma – Presence of PAS positive glycogen &
keratin.

47. SPITZ NEVI
(benign juvenile melanoma )
• Spindle &/or epitheloid cell nevus.
• Children & young adults
• Head & neck and extremities
• Solitary dermal dome shaped small
pink nodule
• Majority – Compound , 20%
intradermal, 5-10% junctional

48. Microscopy
• Small , symmetric, well circumscribed.
• epidermis shows hyperplasia &
elongated rete ridges .
• Nevus cell - Spindle cells & Epitheloid cells
• Arrayed as epidermal nests grouped in a vertical orientation
(bunches of bananas or raining down pattern), with clefting
artifact.
• little or no pagetoid spread pattern.

49. • Maturation of the cells with increasing depth.
• Bizarre giant cells may be seen.
• Presence within the epidermis of red globules, form large
bodies through coalescence – Kamino Bodies , apoptotic
degenerating melanocytes.
• Little or no melanin.
• At the dermal base - no mitoses
• Lymphocytic infiltration in dermis

50. • Variants:
1. Desmoplastic
2. Hyalinizing
3. Angiomatoid

51. large cells, with abundant amphophilic
cytoplasm, which may be spindled or
polygonal in shape (large spindle and/or
epithelioid melanocytes
Maturation in a spitz nevus
Globoid eosinophilic bodies (kamino bodies)
PAS & TRICHOME +VE

52. Diagnostic criteria :
Major Criteria Minor Criteria
• Symmetry
• Cell type –large spindle
and epithelioid cells
• Maturation
• Absence of pagetoid
spread
• Kamino bodies
• Junctional cleavage
• Superficial multinucleate
nevus cells
• Perivascular inflammation
• No atypical mitoses
• Solitary nevus cells in deeper
parts

53. • IHC :
 react for HMB45, Melan A/MART1, NK1/C-3 and S100. Of
importance is stratification seen with HMB45- deeper cells stain
intensely than superficial cells, Stratification also seen with
cyclin D1
• D/D –
 Spitzoid melanoma- no maturation, atypical mitoses, pagetoid
spread
 Pigmented spindle cell nevus of reed- seen in blacks & is heavily
pigmented
 Pyogenic granuloma, mastocytoma, juvenile xanthogranuloma,
warts, melanocytic nevi

54. PIGMENTED SPINDLE CELL NEVUS
• 3-6 mm , deeply pigmented , flat or slightly raised papules.
• Young adult, female,- lower extremities.
• Microscopy:
 Symmetrical - proliferation of elongated spindle shaped
heavily pigmented melanocytes in nests at the dermo-
epidermal junctions.
 Vertically oriented & blend with adjacent keratinocytes
rather than forming clefts as in spitz nevi.
 Characteristic accumulation of melanophages.
 Base of the lesion – superficial reticular dermis, show
lymphocytic response.
Kamino bodies may be seen in epidermal compartment

55. D/D-
 Melanoma of the superficial spreading type
Pigmented spindle shaped
nevus
Melonoma
( Superficial spreading)
• Small , symmetric , sharply
demarcated lateral margins.
• Cells Uniform from side to
side
• Descend into the dermis and
mature along nevus line.
•Abnormal mitosis in
uncommon
• Large , asymmetric with lateral
extension.
• Cellular variabilty.
• Little or no maturation
• Common

56. Deep Penetrating Nevus
(Plexiform Spindle Cell Nevus)
• 2nd and 3rd decades
• Head, neck and shoulder
• 2- 9 mm, darkly pigmented
papules and nodules.
• Microscopy –
 Compound type
 Circumscribed and pyramidal in
shape with a broad base abutting
the epidermis and apex towards
the subcutaneous fat.
Composed of loosely arranged
nests or plexiform fascicles
of large pigmented spindle
and epithelioid cells interspersed
with melanophages

57. • Slight nuclear pleomorphism but inconspicuous nucleoli
• Mitoses absent.
• D/D –
Melanoma- Marked atypia
Pagetoid spread
Irregular acanthosis & thinning

58. HALO NEVUS
• Sutton's nevus or nevus depigmentosa
centrifugum
• Pigmented macule surrounded by a depigmented
zone or halo.
• children & young adults, Back.
• Almost any of the types.
• Pathogenesis :
 Circulating Abs against neoplastic melanocytes & inflammatory
cells in the lesion( T lymphocytes both Ag presenting and
cytotoxic)
 The halo - due to cross reaction between a field of melanocytes
and the T cells.

59. Microscopy:
• Common – Inflammatory halo nevus.
• Early - nests of nevus cells embedded in a dense
inflammatory infiltrate in the upper dermis and at the
dermoepidermal jn.
• Later - scattered nevus cells tend to predominate over nests.
apoptotic cells also seen.
• Inflammatory infiltrate -lymphocytes and few melanophages.
• The region of halo nevus at first shows reduction in the
number of melanocytes and later their complete absence
At the periphery of the nevus, the halo is a region where pigment and
melanocytes are reduced or absent, and there may be a subtle
lymphocytic infiltrate at the dermal-epidermal junction

60. Types Inflammation Involution Halo
Inflammatory Present Present Present
Non inflammatory Absent Absent Present
Halo nevus phenomenon Present May involute Absent
Halo dermatitis around
nevus ( Mayerson’s
eczematous nevus)
Temporary
reaction
surrounding a
nevus
Present

61. Recurrent Nevus (Pseudomelanoma)
• A nevus may recur following an incomplete excision
presenting clinically as hyperpigmented lesions
• Confined to the region of the scar and typically presents with
in weeks of the surgical procedure.
• Microscopy:
 Lentiginous and junctional theques above the dermal scar.
 No epidermal ridges.
 Dermal fibrosis.
 Nevus cells are present in the deep dermis and at the edge of
the scar.

62. • HMB45 stains more
prominently in the recurrent nevi
than the original lesion.
• D/D –
RECURRENT MELANOMA -
 Sharp circumscription of the
intraepidermal component,
 Presence of melanocytes in nests
and as single units mostly at the
junction and the typical nevoid
cells of the preexisting dermal
melanocytic nevus beneath a scar
are helpful clues

63. Dysplastic Nevus
• present as macules often with a
central papule, have irregular
border and irregular pigmentation >
5 cms.
• Multiple or solitary
• Adults
• Trunk , lower legs ( Females)
• Shows cytological and architectural
atypia & regarded as intermediate
b/w common nevi and superficial
spreading melanoma

64. Junctional / compound nevi
Architectural Abnormality-
• Shoulder phenomenon
• stromal response with fibrosis.(includes lamellar and
concentric fibroplasias)
• Lentiginous proliferation of melanocytes – not contiguous
nevus cells- spindle / epitheloid
• Random cytological atypia in epidermal component- large
pleomorphic nuclei.
Single & nested melanocytes , lamellar
fibroplasia
Cytologic atypia

65. D/D – Radial growth phase melanoma

66. References
• Levers histopathology of skin
• Weedons pathology
• Mckee
• Sternberg

67. Thank You