Pigmented Skin lesions

Question 1

where are melanocytes derived from and where do they migrate to

Answer 1

derived from neural crest

migrate to skin, uveal tract and leptomeninges

Question 2

describe the role of the Melanocortin 1 gene(MCR1)

Answer 2

encodes MCR1 protein-sits on cell surface, determines balance of pigment in skin and hair, turns phaeomelanin to eumelanin

Question 3

describe what freckles(ephilides) are

Answer 3

patchy increase in melanin pigmentation, reflects clumpy distribution of melanocytes

Question 4

what are actinic lentigines also known as and what are they related to

Answer 4

aka ‘age’ or ‘liver’ spots

related to UV exposure

Question 5

where are actinic lentigines usually seen

Answer 5

face, forearms, dorsal hands

Question 6

describe the morphology of actinic lentigines

Answer 6

epidermis elongated rete ridges, increased melanin and basal melanocytes

Question 7

what are some of the different types of melanocytic naevi

Answer 7

usual type, dysplastic, Spitz, Blue etc.

Question 8

how common are congenital naevus

Answer 8

1-2% babies have them

Question 9

what are the different sizes for small, medium and large congenital naevus and what is increased risk for large naevus

Answer 9

small = <2cm
medium = >2cm <20cm
large= >20cm
10-15% increased risk melanoma

Question 10

describe development of usual type melanocytic naevus in childhood

Answer 10

Junctional naevus = melanocytes proliferate, then form clusters of cells at DEJ

Question 11

describe the development of usual type melanocytic naevus in adolescence/early adulthood

Answer 11

Compound naevus = junctional(DEJ) clusters and groups of cells in dermis

Question 12

describe the development of usual type melanocytic naevus in adults

Answer 12

Intradermal naevus = all junctional activity ceased, entirely dermal

Question 13

describe the appearance of dysplastic naevi

Answer 13

generally >6mm diameter, variegated pigment, border asymmetry

Question 14

describe the clinical setting of sporadic dysplastic naevi

Answer 14

not inherited, one of several atypical naevi, risk of malignant melanoma slightly increased

Question 15

describe the clinical setting of familial dysplastic naevi

Answer 15

strong FH melanoma, autosomal inheritance, lots atypical naevi, lifetime risk melanoma up to 100%

Question 16

what is the host reaction to dysplastic naevi

Answer 16

inflammation and fibrosis

Question 17

how does dysplastic naevi differ to melanoma

Answer 17

epidermis not affected in aevi

Question 18

describe what halo naevi are(rare)

Answer 18

have a peripheral halo of depigmentation, they show inflammatory regression and are overrun by lymphocytes

Question 19

describe what bleu naevi are(rare)

Answer 19

entirely dermal and consist of pigment rich dendritic spindle cells, may have mitosis and mimic melanoma

Question 20

describe what Spitz naevi are(very rare)

Answer 20

consist of large spindle and/or epithelioid cells, may closely mimic melanoma, most entirely benign