1. Diseases of the Skin
by Noel C. Santos, M.D.

2. Definition of Terms
Macroscopic
Macule: flat, circumscribed, discoloration
Papule: elevated solid area  5 mm.
Nodule: elevated solid area > 5 mm.
Plaque: elevated flat-topped > 5mm.
Vesicle: elevated fluid-filled  5 mm.
Bulla: elevated fluid-filled > 5 mm.
Blister: common term for vesicle or bulla
Pustule: discrete, pus-filled raised area

3. Wheal: pruritic, erythematous elevated area resulting
from dermal edema.
Scale: dry, plate-like excrescence resulting from aberrant
cornification.
Lichenification: thick, rough skin with prominent skin
markings, usually 2o repeated rubbing.
Excoriation: linear, traumatic lesion resulting in epidermal
breakage.
Onycholysis: loss of nail substance.

4. Microscopic
Hyperkeratosis: stratum corneum hyperplasia, with
aberrant keratinization.
Parakeratosis: retention of nuclei in stratum corneum,
normal in mucous membranes.
Acanthosis: epidermal hyperplasia
Dyskeratosis: abnormal keratinization below the
stratum granulosum.

5. Papillomatosis: elongation or widening of the dermal
papillae.
Lentiginous: linear pattern of melanocyte proliferation
within the epidermal basal cell layer, reactive or
neoplastic.
Spongiosis: epidermal intercellular edema.
Exocytosis: inflammatory cells infiltrating the
epidermis.

6. Erosion: focal, incomplete loss of epidermis.
Ulceration: focal complete loss of epidermis, may
include dermis and subcutaneous fat.
Vacuolization: vacuoles within or adjacent to cells.

7. ACUTE INFLAMMATORY DERMATOSES
short-lived, mononuclear cell infiltrates with
edema, local tissue damage
URTICARIA (HIVES)
ACUTE ECZEMATOUS DERMATITIS
ERYTHEMA MULTIFORME
ERYTHEMA NODOSUM and ERYTHEMA
INDURATUM

8. URTICARIA (HIVES)
focal mast cell degranulation – histamine
release: pruritus, edema & wheal
Angioedema: dermal & SC fat edema
Perivascular mononuclear infiltrates and edema
Mediated by Ag-specific IgE or IgE-independent
(chemical-induced, PG’s suppression)
Persistent – inability to clear the inciting Ag,
cryptic collagen-vascular disorders,
Hodgkin/s disease

11. Hereditary Angioneurotic Edema
Recurrent attacks
With GIT and laryngeal involvement
Deficient C1 esterase inhibitor
Unregulated activation of the early complement
components

12. ACUTE ECZEMATOUS DERMATITIS
Pathogenetically different w/ same histologic features
Cutaneous delayed-type HS response
Cytokine release and nonspecific recruitment of
inflammatory cells
Gross: pruritic, red, papulovesicular to blistered, oozing
and subsequently crusted, and may evolve into
psoriasis-like scaling plaques
Micro: spongiosis, progressive fluid
accumulation, intraepidermal vesicles; dermal
perivascular lymphocytic infiltrate, mast cell
degranulation, papillary dermal edema; eosinophils
(drug); progressive acanthosis & hyperkeratosis
(chronic)

13. 5 Primary Types of Eczema
CONTACT DERMATITIS
ATOPIC DERMATITIS
DRUG-RELATED ECZEMATOUS DERMATITIS
PHOTO-ECZEMATOUS ERUPTION
PRIMARY IRRITANT DERMATITIS

14. Type Cause Histology Clinical Features
Contact Dermatitis Topically applied Spongiotic dermatitis Itchy or burning;
chemicals; delayed antecedent exposure
HS
Atopic Dermatitis Unknown; heritable ? Spongiotic dermatitis Erythematous plaques
(flexors); + family Hx
Drug-related Systemically Spongiotic dermatitis; Eruption after exposure &
administered eosinophils remits when discontinued
Photo-eruption UV light Spongiotic dermatitis Sun-exposed skin;
phototesting help in
diagnosis
Primary irritant Repeated trauma Spongiotic dermatitis Localized to site of trauma
(rubbing) (early stage)

21. ERYTHEMA MULTIFORME
Uncommon, self-limited HS response
(drugs, infections, systemic disorders)
Extensive epidermal degeneration and necrosis
Due to cell-mediated immune injury (CD8+
cytotoxic T-cells)
Gross: “multiform” –
macules, papules, vesicles, and bullae;
“targets” – red maculopapular with central
vesicular or eroded pallor; symmetric
involvement of extremities

22. ERYTHEMA MULTIFORME (Cont.)
Steven-Johnson syndrome: severe, febrile, erosions and
hemorrhagic crusting
Toxic Epidermal Necrolysis: diffuse mucocutaneous
epithelial necrosis and sloughing; analogous to 30 burns
Micro: dermoepidermal junction & superficial perivascular
lymphocytic infiltrates; dermal edema, focal basal
keratinocyte degeneration and necrosis; Exocytosis with
epidermal necrosis, blistering and shallow erosions;
Target lesions – central epidermal necrosis w/
perivenular inflammation

23. ERYTHEMA NODOSUM/INDURATUM
Panniculitis or inflammation of SC fat
Connective tissue septa – NODOSUM
Fat lobules – INDURATUM
may be Acute or Chronic
Early lesions: necrotizing vasculitis in deep
dermis and subcutis
Eventually develop granulomatous
inflammation and necrosis

24. Erythema Nodosum
Most common, acute onset
Idiopathic or Secondary
(drugs, infections, sarcoidosis, IBD, visceral
malignancy)
Ill-defined, tender erythematous nodules with
fever and malaise
Old lesions flatten, ecchymotic without scarring
while new lesions develop
Bx: early septal widening - edema, fibrin
deposition, neutrophil infiltration (giant cells
& eosinophils) w/o vasculitis

27. Erythema Induratum
Uncommon, unknown cause
Adolescent and menopausal women
Primary vasculitis of SC fat with subsequent
inflammation and necrosis of adipose tissue
Erythematous, slightly tender nodule that
ulcerates and scars
Early: necrotizing vasculitis in deep dermis and
subcutis
Late: fat lobules develop granulomatous
inflammation and necrosis

28. Weber-Christian disease (Relapsing
Febrile Nodular Panniculitis)
Rare form of panniculitis; crops of
erythematous plaques or nodules, mainly
on the legs
Deep lymphohistiocytic infiltrates and giant
cells
Factitial Panniculitis
Self-administered foreign substances
Deep mycotic infections in
immunocompromised
Others: SLE

29. CHRONIC INFLAMMATORY DERMATOSES
Persistent inflammatory disorders
Scaling and shedding (desquamation)
PSORIASIS
LICHEN PLANUS
LUPUS ERYTHEMATOSUS
ACNE VULGARIS

30. PSORIASIS
Common, HLA types (genetic)
New lesions at sites of trauma (Koebner’s phenomenon) –
exogenous stimuli
Damage to stratum corneum – deposition of complement-
fixing Ab’s with 20 complement-mediated injury
Psoriatic endothelium – sensitive to cytokine-induced
expression of adhesion molecules with subsequent
enhanced neutrophil recruitment
Associated with other disorders:
myopathies, enteropathies, AIDS, arthritis

31. PSORIASIS (Cont.)
Gross: well-demarcated salmon pink plaques
with silvery scaling;
elbows, knees, scalp, lumbosacral
area, intergluteal cleft, glans penis
Annular, linear, gyrate or serpiginous
ERYTHRODERMA - total body scaling and
erythema
Nail changes: discoloration, pitting, onycholysis
Pustular psoriasis: rare, life-threatening

33. PSORIASIS (Cont.)
Micro: marked acanthosis with rete elongation, mitoses
above the basal layer; thin or absent stratum
granulosum; extensive overlying parakeratosis
Thin epidermis overlying dermal papillae with dilated
vessels – pinpoint bleeds when overlying scale is
removed (Auspitz sign)
Aggregates of neutrophils in epidermis within small
spongiotic foci in the stratum spinosum (spongiform
pustules) or within the parakeratotic stratum corneum
(Munro’s microabscesses); large, abscess-like

37. LICHEN PLANUS
Unknown cause, self-limited, after 1 to 2 yrs. Leaves
postinflammatory hyperpigmentation
Oral may persist, may become malignant
Cell-mediated immune injury to basal cells
With Koebner’s phenomenon
Gross: pruritic, purple, polygonal papules that may
coalesce into plaques; highlighted by white dots or
lines (Wickham’s striae)
Multiple, symmetrically distributed; hair follicle
epithelium (lichen planopilaris)

40. LICHEN PLANUS (Cont.)
Micro: dense, bank-like dermoepidermal
junction lymphocytic infiltrate with basal cell
degeneration and necrosis; jagged rete “saw-
toothing”
Necrotic basal cells may be sloughed into
inflamed papillary dermis forming colloid or
Civatte bodies
With chronic changes:
acanthosis, hyperkeratosis, thick granular cell
layer

43. LUPUS ERYTHEMATOSUS
Discoid LE – localized cutaneous form w/o systemic
manifestation
Immune complex-mediated and cell-mediated injury to
pigment-containing basal cells
Sun exposure exacerbates the lesion
Gross: ill-defined malar erythema; sharply demarcated
“discoid” erythematous scaling plaques with zones of
irregular pigmentation and small keratotic plugs in hair
follicles

45. LUPUS ERYTHEMATOSUS (Cont.)
Micro: dermoepidermal junction perivascular &
periappendiceal lymphocytic infiltrates
Preferential involvement of SC fat – lupus
profundus
Basal cell vacuolization, epidermal atrophy,
variable hyperkeratosis
Immunofluorescence: granular band along the
dermoepidermal and dermal-follicular
junctions (lupus band test)

47. ACNE VULGARIS
Common, chronic, inflammatory dermatosis affecting hair
follicles
Middle to late teens, males>females
Hormonal changes, alteration in hair follicle
maturations, infection (P. acnes)
Sex hormones, corticosteroid, occupational
exposure, occlusive conditions, heritable component
Lipase degradation of sebaceous oils to highly irritating
fatty acids
Antibiotics and vit. A (retinoic acid)

48. ACNE VULGARIS (Cont.)
Gross: Non-inflammatory – follicular papules with central
black keratin plugs (open comedo); follicular papules
w/ central plugs trapped beneath the epidermis
(closed comedo)
Rupture – Inflammatory: erythematous papules, nodules,
pustules
Micro: lipid & keratin at the midportion of hair follicles,
follicular dilatation; epithelial and sebaceous gland
atrophy
Lymphohistiocytic infiltrates; acute & chronic
inflammation with scar formation

51. BLISTERING (BULLOUS) DERMATITIS
Primary conditions; level of blister
involvement within the skin
SUBCORNEAL: impetigo, p. follaceus
SUPRABASAL: p. vulgaris
SUBEPIDERMAL: bullous pemphigoid, dermatitis
herpetiformis
PEMPHIGUS
BULLOUS PEMPHIGOID
DERMATITIS HERPETIFORMIS

52. PEMPHIGUS
Rare, autoimmune, 4th to 6th decades
Circulating Ab’s to keratinocyte intercellular
cement components that bind and trigger
release of plasminogen activator by
keratinocytes
FOUR variants:
P. vulgaris
P. vegetans
P. foliaceus
P. erythematosus

53. Pemphigus vulgaris
80%; oral mucosa, scalp, face, intertriginous
zones, trunk, pressure points
Superficial and easily ruptures that leave
shallow & crusted erosions
Untreated – uniformly fatal
Pemphigus vegetans
Rare; large, moist verrucous plaques studded
with pustules
Flexural and intertriginous zones

54. Pemphigus foliaceus
More benign, epidemic in S. America
Face, scalp and upper trunk
Extremely superficial bullae leaving only slight
erythema and crusting after rupture
Pemphigus erythematosus
Localized, milder variant of P. foliaceus
Malar zone on the face

56. PEMPHIGUS (Cont.)
Micro: acantholysis leading to intercellular
clefting and broad-based intraepidermal
blisters
P. vulgaris & vegetans: immediately above the
basal layer (suprabasal blisters)
P. foliaceus: stratum granulosum
Immunofluorescence staining around each
keratinocyte (anti-Ig and anti-complement)

61. BULLOUS PEMPHIGOID
Common, autoimmune, elderly
Circulating Ab’s, with complement activation and
granulocyte recruitment, against Ag’s of the lamina
lucida in the epidermal BM
underlying lymphoreticular neoplasm
Gross: tense bullae (up to 8 cm) w/ clear fluid, do not
rupture easily and heal w/o scarring
Micro: subepidermal nonacantholytic blister; linear
dermoepidermal junction fluorescence; superficial
perivascular infiltrates

64. DERMATITIS HERPETIFORMIS
Rare, 3rd to 4th decade, m>f
specific HLA types & celiac disease
Skin & GI lesions respond to gluten-free diet
Immune complex deposition in the skin
Anti-gliadin Ab’s cross reacting with junction anchoring
components (reticulin)
Granular IgA deposits dermal papillae tips
Gross: pruritic, urticarial plaques & vesicles, symmetric
(extensors, upper back & buttock)

66. DERMATITIS HERPETIFORMIS (Cont.)
Micro: neutrophils & fibrin accumulate in the
tips of dermal papillae (microabscesses)
with overlying basal vacuolization;
microscopic blisters coalescing to large
subepidermal blisters

68. NONINFLAMMATORY BLISTERING DISEASES
Primary disorders with vesicles and bullae
NOT mediated by inflammatory mechanisms
PORPHYRIA
EPIDERMOLYSIS BULLOSA

69. PORPHYRIA
Inborn or acquired disturbances of porphyrin
metabolism
Unknown pathogenesis
Urticaria and vesicles exacerbated by sun
exposure; heals w/o scarring
Subepidermal vesicles with marked superficial
dermal vascular thickening

70. EPIDERMOLYSIS BULLOSA
Blistering at pressure sites and trauma
TYPES:
JUNCTIONAL: blistering at the lamina lucida
DYSTROPHIC: scarring, blistering beneath the lamina
lucida due to defective anchoring fibrils
SIMPLEX: epidermal basal cell degeneration

71. INFECTION and INFESTATION
VERRUCAE (WARTS)
MOLLUSCUM CONTAGIOSUM
IMPETIGO
LEPROSY
SUPERFICIAL FUNGAL INFECTIONS
ARTHROPOD-ASSOCIATED LESIONS

72. VERRUCAE (WARTS)
Common, HPV, direct contact
V. Vulgaris: most common, dorsum of hand; gray-white to
tan, flat to convex, up to 1 cm. papules with rough
pebbly surface
V. plana (flat wart): face or dorsum of hand;
flat, smooth, small, tan papules
V. plantaris or palmaris: rough, scaly, up to 2 cm; may
coalesce, confused with callous
Condyloma acuminatum (Anogenital and Venereal Warts):
soft, tan, cauliflower-like
Micro: undulant (verrucous) epidermal hyperplasia and
koilocytosis

77. MOLLUSCUM CONTAGIOSUM
Common, poxvirus, direct contact
Gross: firm, pruritic, pink to skin-colored,
umbilicated papules, up to 2 cm, trunk &
anogenital regions
Cheezy material with molluscum bodies
expressed from central umbilication
Micro: cuplike verrucous epidermal hyperplasia
with molluscum bodies (large eosinophilic
cytoplasmic inclusions in the stratum
granulosum or corneum)

81. IMPETIGO
Streptococcal & Staphylococcal infection
erythematous macule progressing to small
papules and eventually shallow erosion with
honey-colored crust
Micro: subcorneal pustules filled with
neutrophils and Gm+ cocci; dermal
inflammation
Pustule rupture releases serum and necrotic
debris to form the crust

84. LEPROSY
Slowly progressive, unsightly & disabling
deformities, peripheral neural sensory deficits
Aerosol transmission, bipolar disease
TUBERCULOID: granulomas, (+) 48-hr lepromin test
LEPROMATOUS: anergic to lepromin, nodular lesions
with macrophages stuffed with bacilli, may coalesce
– leonine facie

89. SUPERFICIAL FUNGAL INFECTIONS
Dermatophytes; confined to nonviable stratum corneum;
by location
Reactive epidermal changes similar to mild eczematous
dermatitis
Tinea capitis: asymptomatic hairless patches, mild
erythema, crusting and scales
Tinea barbae: beard area among adult men
Tinea corporis: excessive heat & humidity, infected
animals, chronic infection of the feet/nails;
expanding erythematous plaque with elevated
scaling border – “ringworm”

90. FUNGAL INFECTIONS (Cont.)
Tinea cruris: inguinal areas among obese, warm
weather; moist patches with raised scaling borders
Tinea pedis (Athlete’s foot): erythema & scaling in the
webbed spaces, 2O bacterial infections
Onychomycosis: discoloration, thickening and
deformity of the nail plate
Tinea versicolor: Malassezia furfur, upper trunk, vari-
sized hyper- or hypopigmented macules with
peripheral scale

95. ARTHROPOD-ASSOCIATED LESIONS
Bites, stings, infestations
Reactions: trivial to fatal
Gross: urticarial, inflamed papules or nodules,
expanding erythematous plaques (erythema
migrans)
Direct irritant effect
Immediate IgE-mediated or delayed cell-
mediated HS Rxn
Specific effects of venom
Associated with secondary invaders

98. SCABIES
Pruritic caused by mite Sarcoptes scabiei
Female burrows beneath the stratum corneum –
linear, poorly defined furrows: interdigital
skin, palms, wrists, periareolar area, scrotal
folds

99. PEDICULOSIS
Pruritic, caused by louse: insect or eggs attach to hair
shafts
May be complicated by impetigo with lymphadenopathy;
urticaria-like
Excoriations and hyperpigmentation
Micro: wedge-shaped dermal perivascular
lymphohistiocytic and eosinophilic infiltrates; central
zone of epidermal necrosis w/ birefringent insect
mouth parts; florid inflammatory infiltrates or
spongiosis – intraepidermal blisters

100. DISORDERS OF PIGMENTATION AND
MELANOCYTES
VITILIGO
FRECKLE (EPHELIS)
MELASMA
LENTIGO
NEVOCELLULAR NEVUS (PIGMENTED
NEVUS, MOLE)
DYSPLASTIC NEVI
MELANOMA

101. VITILIGO
Irregular, well-demarcated macules devoid of
pigmentation
Autoimmunity (melanocyte autoAb’s, T-cell
abnormalities); neurohormonal factors; toxic
intermediates in melanin synthesis
Micro: loss of melanocytes

102. FRECKLE (EPHELIS)
Pigmented lesions: tan-red to brown macules
occurring after sun exposure, fading and
recurring with subsequent cycles of winter
and summer
Micro: normal melanocyte number, ?slight
hypertrophy; increased melanin within basal
keratinocytes

103. MELASMA
Masklike facial hyperpigmentation
Hyperestrogenic states, fades postpartum
Gross: blotchy, irregular, ill-defined macules; accentuated
by sunlight
Enhanced melanin transfer from melanocytes to other cell
types w/ subsequent accumulation
Micro: increased melanin deposition in basal layers
(epidermal type); papillary dermal macrophage
phagocytosis of melanin released from the epidermis –
pigment incontinence (dermal type)

104. LENTIGO
Benign, hyperpigmented macules, do not
darken with sun exposure
Unknown etiology and pathogenesis
Micro: linear basal hyperpigmentation due to
melanocyte hyperplasia; with elongation and
thinning of rete ridges

105. NEVOCELLULAR NEVUS
Group of congenital or acquired melanocyte neoplasm
Well-demarcated, tan-brown papules
Melanocytes derive from basal dendritic cells that
differentiate into round-to-oval cells with uniform
nuclei and prominent nucleoli
Natural History:
Begin as well-defined nests along the dermoepidermal
junction (junctional nevi); lentigo-like (lentiginous)
melanocyte proliferation
Extension of melanocytes forms nests within both
dermis and epidermis (compound nevi)

106. NEVOCELLULAR NEVUS (Cont.)
Lost epidermal component resulting in
dermal nevi
Progressive dermal downgrowth, nevus cells
undergo maturation to resemble neural
tissue
Variants:
Congenital nevus
Blue nevus
Spindle & Epithelioid cell (Spitz) nevus
Halo nevus
Dysplastic nevus

107. Nevus Variant Diagnostic Architectural Features Diagnostic Cytologic Clinical Significance
Features
Congenital nevus Deep dermal, SC growth around Same as ordinary acquired At birth; large variants
adnexae, neuro-vascular bundles nevi have increased melanoma
& blood vessel walls risk
Blue nevus Non-nested dermal infiltration, Highly dendritic, heavily Black-blue nodule;
often with fibrosis pigmented nevus cells confused with melanoma
Spitz’s nevus Fascicular growth Large, plump cells with Children; red-pink nodule;
pink-blue cytoplasm; confused with
fusiform hemangioma
Halo nevus Lymphocytic infiltration Identical to ordinary Immune response vs
surrounding nevus cells acquired nevus nevus cells & surrounding
normal melanocyte
Dysplastic nevus Large, coalescent intraepidermal Cytologic atypia Potential precursor of
nests malignant melanoma

111. DYSPLASTIC NEVUS
Autosomal dominant or sporadic
Larger than acquired nevi; as hundreds of
irregular macules/plaques with pigment
variegation in both sun-exposed and
nonexposed skin
Micro: cytologic and architectural atypia;
enlarged & fused epidermal nevus cell
nests, lentiginous hyperplasia, linear dermo-
epidermal junction fibrosis, pigment
incontinence

114. MELANOMA
Sun exposure, lightly pigmented individuals, hereditary
component
Pruritic, variegated, irregular maculopapular lesions;
CHANGE IN COLORATION
Initially extends horizontally within the epidermis and
superficial dermis (RADIAL GROWTH PHASE); don’t
metastasize – LENTIGO MALIGNA and SUPERFICIAL
SPREADING
VERTICAL GROWTH PHASE – extension into the deep
dermis, loss of cellular maturation, dev’t of the capacity
to metastasize

115. MELANOMA (Cont.)
Clinical behavior & probability of metastasis –
characteristics and depth of invasion of the
vertical growth; mitotic rates and degree of
lymphocytic infiltrates
Micro: melanoma cells – larger than nevus
cells, irregular nuclei, prominent eosinophilic
nucleoli; grow as loose nests lacking
melanocyte maturation

121. BENIGN EPITHELIAL TUMORS
biologically inconsequential lesions derived
from keratinocytes or skin appendages
SEBORRHEIC KERATOSIS
ACANTHOSIS NIGRICANS
FIBROEPITHELIAL POLYP
EPITHELIAL CYST (WEN)
KERATOACANTHOMA
ADNEXAL (APPENDAGE) TUMORS

122. SEBORRHEIC KERATOSIS
Spontaneous lesions; trunk, smaller facial lesions
(dermatosis papulosa nigra)
Large number as part of paraneoplastic syndrome (sign of
Leser-Trelat) due to tumor elaboration of growth
factors]
Gross: uniform, tan-brown, velvety/granular, round
plaques, keratin-filled plugs
Micro: exophytic, hyperplasia of basaloid cells,
hyperkeratosis, keratin-filled “horn cysts”

126. ACANTHOSIS NIGRICANS
Thick hyperpigmented zones in flexural areas
Associated with benign or malignant conditions
elsewhere in the body
BENIGN: 80%, childhood through puberty, autosomal
dominant, obesity or endocrine disorders, part of rare
congenital disorders
MALIGNANT: middle-aged & older, occult
adenocarcinoma
Micro: hyperkeratosis, prominent rete ridges, basal
hyperpigmentation w/o melanocyte hyperplasia

127. FIRBOEPITHELIAL POLYP
Acrochordon, squamous papilloma, skin tag
Soft, flesh-colored attached by slender stalk
with fibrovascular core covered by benign
epidermis
Associated with pregnancy, diabetes or
intestinal polyposis

128. EPITHELIAL CYSTS
Well-circumscribed, firm, SC nodules
Downgrowth and cystic expansion of the epidermal and
follicular epithelium
Micro: based on cyst wall characteristic
Epidermal Inclusion Cyst: normal epidermis
Pilar (Trichilemmal) Cyst: follicular epithelium w/o
granular cell layer
Dermoid Cyst: epidermis w/ multiple skin
appendages, hair follicles
Steatocystoma multiplex: sebaceous gland ductal
epithelium w/ numerous compressed sebaceous
lobules

132. KERATOACANTHOMA
Spontaneously heal, rapidly growing, sun-exposed
Gross: flesh-colored, superficial, with central keratin-filled
craters, face/hands
Micro: cup-shaped epithelial proliferations w/ atypical
cells, enclose central keratin-filled plug.
Pattern of keratinization recapitulates hair follicle (no
granular cell layer)
Minimal inflammation during rapid proliferative phase;
evolves – dermal inflammation and fibrosis; eventually
regress & disappear

136. ADNEXAL (APPENDAGE) TUMORS
Benign neoplasms, few malignant variants;
Mendelian pattern; indicate visceral
malignancy (Cowden’s syndrome – multiple
trichilemmomas with breast Ca)
Single or multiple, nondescript papules and
nodules, site predilection
Ex:
Cylindromas, Syringomas, Trichoepitheliomas,
Trichilemmomas, Sebaceous Gland
Adenoma/Adenocarcinoma

139. PREMALIGNANT AND MALIGNANT EPIDERMA
TUMORS
ACTINIC KERATOSIS
BOWEN’S/BOWENOID LESIONS and
ERYTHROPLASIA OF QUEYRAT
SQUAMOUS CELL CARCINOMA
BASAL CELL CARCINOMA
MERKEL CELL CARCINOMA

140. ACTINIC KERATOSIS
Premalignant dysplastic lesion, chronic sun exposure;
ionizing radiation, hydrocarbons, and arsenicals
Gross: tan-brown, red or flesh-colored, rough consistency,
cutaneous horns
Micro: cytologic atypia in the lower epidermis, parabasal
cell hyperplasia, dyskeratosis; hyperkeratosis,
parakeratosis; epidermal atrophy; dermis is thick with
blue-gray elastic fibers (elastosis)

144. CARCINOMA IN-SITU
Full thickness epidermal cytologic atypia
(Bowen’s disease; Bowenoid papulosis;
Erythroplasia of Queyrat)
Perineal/groin area with erythematous patches;
leukoplakia; well-demarcated, red, scaling
plaques
Micro: entire thickness of epidermis exhibits
cytologic nuclear atypia

145. SQUAMOUS CELL CARCINOMA
Most common; sunlight/UV light directly
damages DNA & exerts immuno-suppressive
effect to Langerhans’ cells; industrial
carcinogens, chronic skin ulcers, old burn
scars, draining osteomyelitis, ionizing
radiation, tobacco or betel nut chewing
Immunosuppression; xeroderma pigmentosum;
HPV infection

146. SQUAMOUS CELL CARCINOMA (Cont.)
Gross: nodular, variably
hyperkeratotic, ulcerates; leukoplakia
(mucosal surface)
May metastasize to regional LN
Micro: from well differentiated to highly
anaplastic with necrosis & abortion
keratinization

149. BASAL CELL CARCINOMA
Common, slow-growing, sun-exposed and rarely
metastasize
Immunosuppression & xeroderma pigmentosum
Gross: pearly papules or expanding plaques;
may be pigmented; ulcerate with extensive
local invasion “rodent ulcer”
Micro: basal cell proliferation extending deeply
into the dermis; superficial or nodular

154. MERKEL CELL CARCINOMA
Rare, neural crest derived Merkel cells (tactile
sensation)
Potentially lethal; small, round malignant cells
containing neurosecretory type cytoplasmic
granules
Resemble small cell Ca of the lung

155. TUMORS OF THE DERMIS
BENIGN FIBROUS HISTIOCYTOMA
DERMATOFIBROSARCOMA PROTUBERANS
XANTHOMAS
DERMAL VASCULAR TUMORS

156. BENIGN FIBROUS HISTIOCYTOMA
Indolent neoplasms of dermal fibroblasts &
histiocytes
Unknown cause, antecedent trauma and
aberrant healing
Gross: tan-brown, firm papules, may be tender;
lateral compression exert dimpling
Micro: dermatofibroma – spindle shaped
fibroblasts, unencapsulated in the mid-dermis
extending to SC fat

157. DERMATOFIBROSARCOMA PROTUBERANS
Well-differentiated, slow-growing fibrosarcoma;
locally aggressive but rarely metastasize
Gross: firm solid nodules arising as
protuberant, ulcerated aggregates within an
indurated plaque
Micro: radially oriented (storiform) fibroblasts;
scanty mitosis; thin overlying epidermis with
extension into SC fat

161. XANTHOMAS
Not true neoplasm, focal accumulation of foamy
histiocytes
Idiopathic or Secondary (familial or acquired
hyperlipidemias, lymphoproliferative
disorders)
Types (gross & hyperlipidemia):
Eruptive Xanthoma: sudden showers of
yellow papules that wax & wane w/
plasma triglycerides & lipid levels
Tuberous Xanthoma: yellow, flat-to-round
nodules over the joints

162. XANTHOMAS (Cont.)
Tendinous Xanthoma: yellow nodules over
the Achilles tendon and finger extensor
tendons
Plane Xanthoma: linear yellow lesions in skin
folds (palmar creases); 1O biliary cirrhosis
Xanthelasma: soft yellow plaques on the
eyelids
Micro: dermal aggregates of macrophages with
vacuolated cytoplasm containing
cholesterol, phospholipids, and triglycerides

165. DERMAL VASCULAR TUMORS
Hemangiomas, vascular malignant
tumors, Kaposi’s sarcoma and angiomatosis

168. TUMORS OF CELLULAR IMMIGRANTS TO THE
SKIN
Proliferative disorders of cells arising
elsewhere but which homed to the skin
HISTIOCYTOSIS X
MYCOSIS FUNGOIDES (CUTANEOUS T-CELL
LYMPHOMA)
MASTOCYTOSIS

169. HISTIOCYTOSIS X
Cutaneous form – solitary or multiple papules or nodules;
scaling erythematous plaques resembling seborrheic
dermatitis
Histo: variable numbers of eosinophils and different
patterns:
Diffuse dermal infiltrates of mononuclear cells with
bland, indented nuclei
Similar cells clustered to resemble granulomas
Dermal infiltrates composed of mononuclear cells
with foamy cytoplasm
Birbeck granules, CD1 Ag’s – Langerhans’ cell derivation

170. MYCOSIS FUNGOIDES
Cutaneous T-cell Lymphoma, 3 patterns
Mycosis Fungoides (MF)
MF d’emblee: nodular eruptive variant
Adult T-cell leukemia or lymphoma: aggressive
course, HTLV-1
Lymphoproliferative disorder arising from the
skin & eventually seed the blood (Sezary’s
syndrome) and evolve into more generalized T-
cell leukemia or lymphoma

171. MYCOSIS FUNGOIDES
Gross: eczema-like lesions evolving into scaly, red-
brown patches or plaques; to nodules (nodular
cutaneous growth – deep dermal invasion; onset
of LN & visceral involvement)
Micro: Sezary-Lutzner cell – malignant CD4-positive
(T-helper) cell with hyperconvoluted or
“cerebriform” nucleus; band-like dermal
infiltrates with invasion of single cells or small
clusters into the epidermis (Pautrier’s
microabscess)

176. MASTOCYTOSIS
Rare, cutaneous (visceral) mast cell
proliferation; degranulation (histamine and
heparin)
Pruritus & flushing – specific
foods, temperature, alcohol, certain drugs
Dermal edema & erythema (wheal) when skin
(Darier’s sign) or normal skin
(dermatographism) is rubbed
Epistaxis or GI bleeding

177. MASTOCYTOSIS (Cont.)
Urticaria pigmentosa (50%) exclusively
cutaneous, favorable prognosis, children;
10% adults, systemic, poorer prognosis
Gross: multiple, round-to-oval, nonscaling, red-
brown papules & plaques
Micro: dermal fibrosis, edema, eosinophils and
mast cells

183. That’s all folks!!!
Thank you very much!!!
Good morning!!!