Pathoma - Skin - Tumors, Pigment, Infection

Question 1

Describe the appearance of seborrheic keratosis

Answer 1

Flat, greasy, pigmented squamous cell proliferation with keratin-filled cysts (horn cysts)

Looks “stuck on”

Question 2

Describe histology of seborrheic keratosis

Answer 2

Keratin psuedocysts

Question 3

What is Leser-Trelat sign?

Answer 3

Sudden onset of multiple seborrheic keratoses

Suggestive of underlying carcinoma of the GI tract

Question 4

What are the two disease associations of acanthosis nigricans

Answer 4

Insulin resistance (e.g. diabetes, obesity, Cushing’s)

Malignancy (especially gastric carcinoma)

Question 5

What is the most common skin cancer

Answer 5

Basal cell carcinoma

Question 6

Describe the apperance of basal cell carcinoma

Answer 6

Elevated nodule with central, ulcereated crater surrounded by dilated vessels (rolled borders)

“pink, pearl-like papule”

Question 7

Describe histology of basal cell carcinoma

Answer 7

Nodules of basal cells with peripheral palisading

Question 8

Prognosis of basal cell carcinoma?

Answer 8

Good - metastasis is rare

Question 9

What is xeroderma pigmentosum

Answer 9

Autosomal recessive defect in enzymes required for nucleotide repair

Inability to repair pyrimidine dimers caused by UV rays

Question 10

Describe the histology of squamous cell carcinoma

Answer 10

Keratin pearls

Question 11

Describe common location of basal cell carcinoma vs. squamous cell carcinoma

Answer 11

Basal cell - upper lip

Squamous cell - lower lip

Question 12

What is actinic keratosis and what is an important complication?

Answer 12

Scaly plaque that is a precursor of squamous cell carcinoma

Question 13

What is keratoacanthoma?

Answer 13

Well-differentiated squamous cell carcinoma that develops rapidly and regresses spontaneously

Question 14

What embryonic structure are melanocytes derived from?

Answer 14

Neural crest

Question 15

Describe synthesis and distribution of pigment

Answer 15

Melanocytes synthesize melanin in melanosomes using tyrosine, and then pass melanosomes to keratinocytes

Question 16

What is the defect in vitiligo?

Answer 16

Localized loss of skin pigmentation due to autoimmune destruction of melanocytes

Question 17

Describe the defect in albinism

Answer 17

Congenital lack of pigment due to enzyme defect (e.g. tyrosinase) that impairs melanin production

Question 18

What is the cause of freckles?

Answer 18

Increased number of melanosomes (melanocytes are NOT increased)

Question 19

What is melasma and its associations

Answer 19

Mask-like hyperpigmentation of the cheeks

Associated with pregnancy and oral contraceptives

Question 20

Differentiate between junctional, compound, and intradermal nevus

Answer 20

Junctional - nest of melanocytes at the dermal-epidermal junction

Compound - nests at the junction grow into the dermia

Dermal - dermal-epidermal nest is lost and there are just melanocytes within the dermis

Question 21

Appearance of junctional vs. dermal nevus

Answer 21

Junctional - flat macules

Dermal - papular

Question 22

What are the ABCs of melanoma

Answer 22

A - Asymmetry

B - irregular Borders

C - Color is not uniform

D - Diameter > 6 mm

E - Evolution over time

Question 23

Describe radial vs. vertical growth of melanoma

Answer 23

Radial - horizontal growth along epidermis and superficial dermis (low risk of metastasis)

Vertical - growth into deep dermis (increased risk of metastasis - Breslow thickness)

Question 24

Cause of Staphylococcal scalded skin syndrome

Answer 24

Exfolatin A and B toxin result in epidermolysis of stratum granulosum

Question 25

Differentiate staph scalded skin syndrome from toxic epidermal necrolysis

Answer 25

SSSS - epidermolysis at stratum granulosum (superifical skin sloughing)

TEN - epidermolysis at dermal-epidermal junction (deeper sloughing)

Question 26

Describe histology of Molluscum contagiusum

Answer 26

Cytoplasmic inclusions within keratinocytes (molluscum bodies)