Dermatopathology (Part 1 of 4)

Question 1

what is the most common pigmented lesion of childhood?

Answer 1

freckles

Question 2

when and where are freckles seen?

Answer 2

after sun exposure and in sun exposed areas

Question 3

how do freckles change over time?

Answer 3

they fade and darken with season changes–> change in the degree of pigmentation

Question 4

what is hyperpigmentation?

Answer 4

an increase in melanin pigment in basal keratinocytes

Question 5

if you are seeing freckle like lesions in non-sun exposed areas, what might you be seeing?

Answer 5

cafe au lait spots

Question 6

how are cafe au lait spots in neurofibromatosis different from freckles?

Answer 6

they are larger and arise independently of sun exposure; they contain aggregated melanosomes (macromalanosomes) in the cytoplasm of their melanocytes

Question 7

what are malanocytes derived from?

Answer 7

NCCs

Question 8

what is lentigo?

Answer 8

a benign localized hyperplasia of melanocytes–> no sex or racial predilection; cause unknown

Question 9

when are lentigo’s initiated?

Answer 9

in infancy and childhood

Question 10

how would you describe the morphological features of a lentigo?

Answer 10

5-10 mm, oval, tan-brown macules or patches

Question 11

what happens to lentigos when they are exposed to sunlight?

Answer 11

nothing- they do not darken

Question 12

what does a lentigo look like histologically?

Answer 12

linear (nonnested) melanocytic hyperplasia

Question 13

where are lentigos restricted to?

Answer 13

restricted to the cell layer immediately above the basement membrane

Question 14

what are acral sites?

Answer 14

palms and soles of the feet

Question 15

what is the colloquial term for a melanocytic nevus?

Answer 15

a mole

Question 16

how are melanocytic nevi acquired?

Answer 16

by activating mutations in components of the RAS or BRAF signaling pathway–> limited period of proliferation

Question 17

what causes the proliferation seen in a melanocytic nevus to be in a permanent growth arrest?

Answer 17

a disruption to the p16/INK4a

Question 18

what is the p16/INK4a’s function normally?

Answer 18

it inhibits CDK4 and CDK6

Question 19

how would you describe the morphological features of a melanocytic nevus?

Answer 19

usually less than 6 mm, tan-brown, and uniformly pigmented; flat macules or elevated papules with well-defined borders

Question 20

what are the earliest melanocytic nevi lesions known to be?

Answer 20

junctional nevi

Question 21

what are junctional nevi?

Answer 21

aggregates or nests of round cells that grow along the dermoepidermal junction

Question 22

what could junctional nevi progress to?

Answer 22

compound nevi

Question 23

what are compound nevi?

Answer 23

nests or cords that grow into the underlying dermis (nests are in the epidermis and the dermis)

Question 24

what can compound nevi progress to?

Answer 24

intradermal nevi

Question 25

what are intradermal nevi?

Answer 25

there are no epidermal nests, and they are usually older lesions

Question 26

which benign melanocytic nevi has the most melanin?

Answer 26

the more superficial one

Question 27

what does the deepest evidence of a benign melanocytic nevus look like?

Answer 27

fusiform--> fascicles resembling neural tissue--> neurotization

Question 28

what is helpful when trying to differentiate between a benign nevi and melanoma?

Answer 28

the metamorphosis of the nevi into something that resembles neural tissue in benign nevi

Question 29

which nevi are often more elevated?

Answer 29

compound and dermal

Question 30

which nevi are nice and flat?

Answer 30

junctional

Question 31

what are the diagnostic architectural features of a dysplastic nevus?

Answer 31

coalescent intraepidermal nests

Question 32

what are the cytologic features of a dysplastic nevus?

Answer 32

cytologic atypia

Question 33

what is the clinical significance of a dysplastic nevus?

Answer 33

it is a potential marker or precursor of melanoma

Question 34

what is dysplastic nevus syndrome?

Answer 34

an autosomal dominant disorder that may cause development of several melanomas at multiple sites

Question 35

what gene is involved in dysplastic nevus syndrome?

Answer 35

CDKN2A or CDK4 gene

Question 36

dysplastic nevi often acquire activating mutations in what genes?

Answer 36

NRAS and BRAF genes

Question 37

what are the histological features of dysplastic nevi?

Answer 37

they are larger than acquired nevi, >5mm--> could be hundreds; variegated pigmentation, irregular borders of lesions

Question 38

what are the atypical features seen in dysplastic nevi?

Answer 38

large nuclei, irregular angulated nuclear contour, and hyperchromasia

Question 39

microscopically, dysplastic nevi usually involve what?

Answer 39

both the epidermis and the dermis

Question 40

what is the most deadly of all skin cancers?

Answer 40

melanoma

Question 41

what is melanoma strongly linked to?

Answer 41

acquired mutations caused by exposure to UV radiation in sunlight (DNA damage)

Question 42

the increased incidence by decrease in death rates of melanoma may reflect what?

Answer 42

the effectiveness of immune checkpoint inhibitor therapy