Melanocytic Lesions

Question 1

which gene determines the balance of pigment in skin and hair

Answer 1

melanocortin 1 receptor gene (MC1R)

Question 2

role of MC1R

Answer 2

turns phaeomelanin into eumelanin

Question 3

defective copies of MC1R causes

Answer 3

• one copy causes freckling

- two copies causes red hair and freckles

Question 4

define freckles (ephilides)

Answer 4

patchy increase in melanin pigmentation, reflecting clumpy distribution in melanocytes

Question 5

when do actinic lentigines occur

Answer 5

age or liver spots
related to UV exposure
common on face, forearms and dorsal hands

Question 6

pathology of actinic lentigines

Answer 6

epidermis elongated rete ridges and increase in melanin and basal melanocytes

Question 7

list the four types of melanocytes naevi

Answer 7

• congenital melanocytic naevi
• usual type acquired naevi
• dysplastic naevi
• rarer naevi

Question 8

define congenital melanocytic naevi

Answer 8

birth mark

large lesions at risk of developing into melanoma

Question 9

describe usual type acquired naevi

Answer 9

during infancy the melanocyte : keratinocyte ratio breaks down and there is formation of this benign lesion

Question 10

what increases the risk of getting usual type acquired naevi

Answer 10

immunosuppression

Question 11

naevus development stages

Answer 11

1. junctional naevus (childhood)
2. compound naevus (adolescence/early adulthood)
3. intradermal naevus (adulthood)

Question 12

describe the naevus development

Answer 12

clusters of cells at DEJ
move into dermis
entirely dermal

Question 13

define dysplastic naevi

Answer 13

naevi that are above 6mm in diameter

Question 14

presentation of dysplastic naevi

Answer 14

• border asymmetry
• atypical architecture and cells
• host reaction is common

Question 15

two clinical settings that dysplastic naevi can develop

Answer 15

1. sporadic

2. familial

Question 16

describe sporadic dysplastic naevi

Answer 16

not inherited, can just have one to several atypical naevi

Question 17

describe familial naevi

Answer 17

strong family history of melanoma

autosomal inheritance

Question 18

list of rarer naevi

Answer 18

halo naevi
blue naevi
spitz naevi

Question 19

describe halo naevi

Answer 19

peripheral halo of depigmentation, inflammatory regression

Question 20

describe blue naevi

Answer 20

• entirely dermal consisting of pigment-rich dendritic spindle cells (failure of migration of melanocytes)
• unchanging lesion that is dense and dark pigmentation

Question 21

describe spitz naevus

Answer 21

under 20 years
large spindle and/or epitheloid cells
pink colour from vasculature
malignant variant called spitzoid