Pathology of pigmented lesions

Question 1

What does the MC1R gene code for?

Answer 1

Melanocortin 1 receptor proteins

Question 2

What is the function of MC1R proteins?

Answer 2

Turns phaeomelanin into eumelanin and thus determines the balance of pigment in the skin and hair

Question 3

What colour does eumelanin colour hair?

Answer 3

Anything but red

Question 4

What colour does phaeomelanin colour hair?

Answer 4

Red

Question 5

What is caused by 1 defective MC1R gene?

Answer 5

Freckling

Question 6

What is caused by 2 defective copies of the MC1R gene?

Answer 6

Red hair
Freckling

Question 7

What is the medical name for freckles?

Answer 7

Ephilides

Question 8

What are freckles?

Answer 8

Patchy clumps of melanin pigmentation, usually brought on by UV exposure and genetics (MC1R)

Question 9

What are other names for actinic lentigines?

Answer 9

Solar lentigines
Age spots
Liver spots

Question 10

What are the most common places to get actinic lentigines?

Answer 10

Face
Forearms
Dorsal hands

Question 11

What are actinic lentigines?

Answer 11

Groups of increased melanin and basal melanocytes, related to sun exposure (Melanin overproduction)

Question 12

What condition is shown?

Answer 12

Actinic lentigines

Question 13

What is the medical term for a mole?

Answer 13

Naevus

Question 14

What are some types of melanocytic naevi?

Answer 14

Congenital
Dysplastic
Spitz
Blue
Halo

Question 15

What are the 3 stages of acquired naevus development?

Answer 15

Junctional naves - Childhood
Compound naves - Adolescence
Intradermal naves - Adulthood

Question 16

What are the features of a junctional naevus?

Answer 16

• Melanocytes proliferate at the basal layer forming clusters of cells at the dermo-epidermal junction
• Tends to be flat or slightly elevated with smooth surface and uniform pigmentation

Question 17

What are the features of a compound naevus?

Answer 17

• Junctional clusters of melanocytes as well as groups of melanocytes moving down into the dermis
• Lesions are slightly elevated or dome shaped and are often pigmented
• Hairs may project from the surface

Question 18

What are the features of an intradermal naevus?

Answer 18

• All junctional activity is ceased, with all melanocyte clusters forming in the dermis
• Usually dome shaped, verrucous (Warty), pedunculated or sessile, often flesh-coloured, occasionally hairy and may display surface telangiectasia

Question 19

How is the size of a congenital naevus classified?

Answer 19

• Small <2cm diameter
• Medium >2cm but <20cm diameter
• > 20cm Giant-garment type lesions

Question 20

What is a risk of large congenital naevi?

Answer 20

10-15% increased risk of melanoma

Question 21

What causes the formation of simple naevi in infancy?

Answer 21

There is usually a breakdown of malenocyte:keratinocyte ration at a number of cutaneous sites, which is thought to be immune related

Question 22

How many naevi does the average person have?

Answer 22

20-30

Question 23

What are the surface features of dysplastic naevi?

Answer 23

> 6mm diameter
Variegated pigment
Asymmetrical border

Question 24

What are the 2 types of dysplastic naevi?

Answer 24

Sporadic
Familial

Question 25

How does sporadic dysplastic naevi present?

Answer 25

Sporadic dysplasic naevi usually affect one to several naevi and slightly increase risk of malignant melanoma

Question 26

How does familial dysplastic naevi present?

Answer 26

Familial dysplastic naevi have a high penetrance in families and cause many atypical naevi, increasing lifetime risk of melanoma up to 100%

Question 27

How will dysplastic naevi show on histology?

Answer 27

- Architectural atypia - Cellular atypia - Fibrosis - Inflammation Unlike in melanoma, the epidermis is not usually effected, however, severe dysplasia may be difficult to distinguish from melanoma in-situ

Question 28

Describe the features of halo naevi

Answer 28

Halo naevi have a peripheral halo of depigmentation. They show inflammatory regression and are overrun by lymphocytes

Question 29

Describe the features of blue naevi

Answer 29

Blue naevi are entirely dermal and consist of pigment rich dendritic spindle cells. The cellular variant may have mitoses and mimic melanoma These look blue due to the light scattering effect

Question 30

Describe the features of Spitz naevi

Answer 30

Spitz naevi usually occur in those under 20 and consist of large spindle and/or epithelioid cells with pink colouration due to prominent vasculature They may closely mimic melanoma, but most are entirely benign

Question 31

What condition is shown?

Answer 31

Halo naevus

Question 32

What condition is shown?

Answer 32

Blue naevus

Question 33

What condition is shown?

Answer 33

Spitz naevus