CH19 - Skin Pathology Flashcards
What is the function of skin?
It is a barrier against environmental insults and fluid loss
What is skin composed of?
an epidermis and dermis
What is the epidermis comprised of?
keratinocytes and has four layers
What are the layers of the epidermis?
1) Stratum basalis 2) Stratum spinosum 3) Stratum granulosum 4) Stratum corneum
What is the stratum basalis?
regenerative (stem cell) layer
What is the stratum spinosum?
Its characterized by desmosomes between keratinocytes
What is the stratum granulosum?
It is characterized by granules in keratinocytes
What is the stratum corneum?
It is characterized by keratin in anucleate cells
What does the dermis consist of?
connective tissue, nerve endings, blood and lymphatic vessels, and adnexal structures (e.g., hair shafts, sweat glands, and sebaceous glands)
What are the inflammatory dermatoses?
1) atopic (eczematous) dermatitis 2) contact dermatitis 3) acne vulgaris 4) psoriasis 5) Lichen Planus
What is atopic (eczematous) dermatitis?
Pruritic, erythematous, oozing rash with vesicles and edema; often involves the face and flexor surfaces
What are flexor surfaces?
Elbow, wrists and knees
What is type 1 hypersensitivity reaction associated with?
asthma and allergic rhinitis
What is contact dermatitis?
Pruritic, erythematous, oozing rash with vesicles and edema
When does contact dermatitis arise?
upon exposure to allergens
What are the allergens for contact dermatitis?
1) Poison ivy and nickel jewelry (type IV hypersensitivity) 2) Irritant chemicals (e.g., detergents) 3) Drugs (e.g., penicillin)
What is the treatment for contact dermatitis?
It involves removal of the offending agent and topical glucocorticoids, if needed.
What is acne vulgaris?
Comedones (whiteheads and blackheads), pustules (pimples), and nodules; extremely common, especially in adolescents
What is acne vulgaris due to?
chronic inflammation of hair follicles and associated sebaceous glands
In acne vulgaris, how are comedones formed?
There is hormone-associated increase in sebum production (sebaceous glands have androgen receptors) and excess keratin production block follicles
What are propionibacterium acnes?
It is infection that produces lipases that break down sebum, releasing proinflammatory fatty acids; results in pustule or nodule formation
What is the treatment for acne vulgaris?
Treatment includes benzoyl peroxide (antimicrobial) and vitamin A derivatives (e.g., isotretinoin), which reduce keratin production.
What is psoriasis?
Well-circumscribed, salmon-colored plaques with silvery scale, usually on extensor surfaces and the scalp; pitting of nails may also be present.
What is psoriasis due to?
excessive keratinocyte proliferation
What is the etiology for psoriasis?
Possible autoimmune etiology
What is psoriasis associated with?
HLA-C
For psoriasis, what happens if there is an environmental trigger?
lesions often arise in areas of trauma (environmental trigger)
What does the histology for psoriasis show?
1) Acanthosis (epidermal hyperplasia) 2) Parakeratosis 3) Collections of neutrophils in the stratum corneum (Munro microabscesses) 4) Thinning of the epidermis above elongated dermal papillae; results in bleeding when scale is picked off (Auspitz sign)
What is parakeratosis?
hyperkeratosis with retention of keratinocyte nuclei in the stratum comeum
What is the treatment for psoriasis?
it involves corticosteroids, UV light with psoralen, or immune-modulating therapy.
What is lichen planus?
Pruritic, planar, polygonal, purple papules often with reticular white lines on their surface (Wickham striae); commonly involves wrists, elbows, and oral mucosa
What does lichen planus commonly involve?
Wrists, elbows and oral mucosa
What does oral involvement of lichen planus manifest as?
Wickham striae
What does histology for lichen planus show?
inflammation of the dermal-epidermal junction with a saw-tooth appearance
What is the etiology for lichen planus?
Etiology is unknown
What is lichen planus associated with?
chronic hepatitis C virus infection
What are the blistering dermatoses?
1) pemphigus vulgaris 2) bullous phemphigoid 3) dermatitis herpetiformois 4) erythema multiforme
What is pemphigus vulgaris?
Its autoimmune destruction of desmosomes between keratinocytes
What is pemphigus vulgaris due to?
IgG antibody against desmoglein (type II hypersensitivity)
What does pemphigus vulgaris present as?
skin and oral mucosa bullae
In pemphigus vulgaris, why is there suprabasal blisters?
Acantholysis (separation) of stratum spinosum keratinocytes (normally connected by desmosomes) results in suprabasal blisters.
In pemphigus vulgaris, why is there a tombstone appearance?
Basal layer cells remain attached to basement membrane via hemidesmosomes - tombstone appearance
In pemphigus vulgaris, why is there shallow erosions with dried crust?
Thin-walled bullae rupture easily (Nikolsky sign), leading to shallow erosions with dried crust.
In pemphigus vulgaris, why is there a fish net pattern?
Immunofluorescence highlights IgG surrounding keratinocytes in a fish net pattern.
What is bullous pemphigoid?
Autoimmune destruction of hemidesmosomes between basal cells and the underlying basement membrane
What is bullous pemphigoid due to?
Its due to IgG antibody against basement membrane collagen
What does bullous pemphigoid present as?
blisters of the skin, oral mucosa is spared 1) Basal cell layer is detached from the basement membrane 2) Tense bullae do not rupture easily; clinically milder than pemphigus vulgaris
In bullous pemphigoid, what does immunofluorescence show?
it highlights IgG along basement membrane (linear pattern)
What is dermatitis herpetiformis?
Autoimmune deposition of IgA at the tips of dermal papillae
What does dermatitis herpetiformis present?
as pruritic vesicles and bullae that are grouped (herpetiform)
Dermatitis herpetiformis has a strong association with what?
celiac disease; resolves with gluten-free diet
What is erythema multiforme?
Hypersensitivity reaction characterized by targetoid rash and bullae
What is the targetoid appearance due to?
central epidermal necrosis surrounded by erythema
Erythema multiforme is most commonly associated with what?
HSV infection
Aside form HSV infections, what do the other associations include?
Mycoplasma infection, drugs (penicillin and sulfonamides), autoimmune disease (eg SLE), and malignancy
What is Steven Johnsons syndrome?
EM with oral mucosa/lip involvement and fever is termed Stevens Johnson syndrome (SJS)
What is toxic epidermal necrolysis?
It is a severe form of SJS characterized by diffuse sloughing of skin, resembling a large bum; most often due to an adverse drug reaction
What are the epithelial tumors?
1) seborrheic keratosis 2) acanthosis nigracans 3) basal cell carcinoma 4) squamous cell carcinoma
What is seborrheic keratosis?
Benign squamous proliferation; common tumor in the elderly
What does seborrheic keratosis present as?
raised, discolored plaques on the extremities or face; often has a coinlike, waxy, stuck-on appearance
What is seborrheic keratosis characterized by?
keratin pseudocysts on histology
What is a sign involved with seborrheic keratosis?
Leser-Trelat sign is the sudden onset of multiple seborrheic keratoses and suggests underlying carcinoma of the GI tract
What is acanthosis nigricans?
Epidermal hyperplasia with darkening of the skin, velvet-like skin; often involves the axilla or groin
What is acanthosis nigricans associated with?
insulin resistance (e.g., non-insulin-dependent diabetes) or malignancy (especially gastric carcinoma)
What is basal cell carcinoma?
Malignant proliferation of the basal cells of the epidermis
What is the most common cutaneous malignancy?
Basal cell carcinoma
What are the risk factors for basal cell carcinoma?
stem from UVB-induced DNA damage and include prolonged exposure to sunlight, albinism, and xeroderma pigmentosum
What does basal cell carcinoma present as?
an elevated nodule with a central, ulcerated crater surrounded by dilated (telangiectatic) vessels, pink, pearl-like papule
What is the classic location for basal cell carcinoma?
Classic location is the upper lip
What does the histology for basal cell carcinoma show?
nodules of basal cells with peripheral palisading
What is the treatment for basal cell carcinoma?
surgical excision; metastasis is rare.
What is squamous cell carcinoma?
malignant proliferation of squamous cells
What is squamous cell carcinoma characterized by?
formation of keratin pearls
What are the risk factors for squamous cell carcinoma?
stem from UVB-induced DNA damage and include prolonged exposure to sunlight, albinism, and xeroderma pigmentosum.
What are the additional risk factors for squamous cell carcinoma?
they include immunosuppressive therapy, arsenic exposure, and chronic inflammation (eg scar from burn or draining sinus tract)
What does squamous cell carcinoma present as?
an ulcerated, nodular mass, usually on the face (classically involving the lower lip)
What is the treatment for squamous cell carcinoma?
it is excision; metastasis is uncommon.
What is a precursor lesion of squamous cell carcinoma and how does it present?
Actinic keratosis and presents as a hyperkeratotic, scaly plaque, often on the face, back, or neck.
What is Keratoacanthoma?
it is well-differentiated squamous cell carcinoma that develops rapidly and regresses spontaneously
How does keratoacanthoma present?
as a cup-shaped tumor filled with keratin debris
What are the disorders of pigmentation and melanocytes?
1) vitiligo 2) albinism 3) Freckle (ephelis) 4) melasma 5) nevus (mole) 6) melanoma
What are melanocytes responsible for?
skin pigmentation
Where are melanocytes located?
They are present in the basal layer of the epidermis.
What are melanocytes derived from?
the neural crest
What do melanocytes do?
Synthesize melanin in melanosomes using tyrosine as a precursor molecule
What do melanocytes do?
They pass melanosomes to keratinocytes
What is vitiligo?
Localized loss of skin pigmentation
What is vitiligo due to?
autoimmune destruction of melanocytes
What happens in albinism?
It is a congenital lack of pigmentation
What is albinism due to?
an enzyme defect (usually tyrosinase) that impairs melanin production
What might albinism involve?
May involve the eyes (ocular form) or both the eyes and skin (oculocutaneous form)
What is there an increased risk for in albinism and why?
Increased risk of squamous cell carcinoma, basal cell carcinoma, and melanoma due to reduced protection against UVB
What is freckle?
(ephelis) small, tan to brown macule; darkens when exposed to sunlight
What is freckle due to?
increased number of melanosomes (melanocytes are not increased)
What is melasma?
mask-like hyperpigmentation of the cheeks
What is melasma associated with?
pregnancy and oral contraceptives
What is nevus?
(mole) benign neoplasm of melanocytes
What is congenital nevus?
it is present at birth; often associated with hair
When do you see acquired nevus?
it arises later in life.
How does a nevus begin?
Begins as nests of melanocytes at the dermal-epidermal junction (junctional nevus);
What is the most common mole in children?
nevus
What is a compound nevus?
When the nevus grows by extension into the dermis
What is an intradermal nevus?
The junctional component is eventually lost resulting in an intradermal nevus, which is the most common mole in adults.
What is the most common mole in adults?
Intradermal nevus
What is a nevus characterized by?
Characterized by a flat macule or raised papule with symmetry, sharp borders, evenly distributed color, and small diameter (< 6 mm)
What might arise from a nevus?
Dysplasia may arise (dysplastic nevus), which is a precursor to melanoma
What is melanoma?
Malignant neoplasm of melanocytes; most common cause of death from skin cancer
What is the most common form of death from skin cancer?
Melanoma
What are the risk factors for melanoma?
They are based on UVB-induced DNA damage and include prolonged exposure to sunlight, albinism, and xeroderma pigmentosum; an additional risk factor is dysplastic nevus syndrome,
What is dysplastic nevus syndrome?
autosomal dominant disorder characterized by formation of dysplastic nevi that may progress to melanoma
What does dysplastic nevus syndrome present as?
a mole-like growth with ABCD
What is the ABCD for a mole like growth in dysplastic nevus syndrome?
1) Asymmetry 2) Borders are irregular. 3) Color is not uniform. 4) Diameter > 6 mm
How is melanoma characterized?
by two growth phases
What are the growth phases that characterize melanoma?
1) radial growth 2) vertical growth
What is the radial growth in melanoma?
It grows horizontally along the epidermis and superficial dermis
For radial growth, what is the risk for metastasis?
low risk of metastasis
What is the vertical growth in melanoma?
It grows vertically into the deep dermis
In vertical growth in melanoma what is the most important prognostic factor in predicting metastasis?
The depth of extension (Breslow thickness) is the most important prognostic factor in predicting metastasis.
What are the variants for melanoma?
1) superficial spreading 2) lentigo maligna melanoma 3) nodular 4) acral lentiginous
What is superficial spreading in melanoma?
most common subtype; dominant early radial growth results in good prognosis
What is the prognosis for superficial spreading in melanoma?
Dominant early radial growth results in good prognosis
What is lentigo maligna melanoma and what is the prognosis?
lentiginous proliferation (radial growth) good prognosis
What is nodular regarding the variant of melanoma and what is the prognosis?
early vertical growth; poor prognosis
What is involved in the Acral lentiginous variant of melanoma?
It arises on the palms or soles, often in dark-skinned individuals; not related to UV light exposure
What is impetigo?
Superficial bacterial skin infection
What is impetigo most often due to?
S. aureus or S. pyogenes
Who does impetigo commonly affect?
children
What does impetigo present as?
erythematous macules that progress to pustules, usually on the face; rupture of pustules results in erosions and dry, crusted, honey-colored serum.
What is cellulitis?
It?s a deeper (dermal and subcutaneous) infection, usually due to S. aureus or S. pyogenes
What does cellulitis present as?
a red, tender, swollen rash with fever
What are the risk factors for cellulitis?
They include recent surgery, trauma, or insect bite.
What can cellulitis progress to?
Can progress to necrotizing fasciitis with necrosis of subcutaneous tissues due to infection with anaerobic flesh-eating bacteria
What happens when cellulitis progresses to necrotizing fasciitis?
1) Production of CO2 leads to crepitus. 2) Surgical emergency
What is staphylococcal scaled skin syndrome?
Sloughing of skin with erythematous rash and fever; leads to significant skin loss
What is staphylococcal scaled skin syndrome due to?
S. aureus infection; where there is exfoliative A and B toxins that result in epidermolysis of the stratum granulosum.
How is staphylococcal scaled skin syndrome distinguished histologically from toxic epidermal necrolysis?
by level of skin separation; separation in TEN (toxic epidermal necrolysis) occurs at the dermal-epidermal junction
What is Verruca?
(wart) Flesh-colored papules with a rough surface
What is verruca due to?
HPV infection of keratinocytes;
What is Verruca characterized by?
koilocytic change
What are common locations for verruca?
Hands and feet
What is molluscum contagiosum?
Firm, pink, umbilicated papules due to poxvirus;
In molluscum contagiosum, what happens to the affected keratinocytes?
it shows cytoplasmic inclusions (molluscum bodies)
In whom does molluscum contagiosum most often arise? Who else does it arise?
in children; also occur in sexually active adults and immunocompromised individuals
