Pathology Of Pigmented Skin Lesions

Question 1

Where do melanocytes migrate from the neural crest to?

Answer 1

Skin
Uveal tract
Lepitomeninges

Question 2

What gene determines the balance of pigment in skin and hair?

Answer 2

MC1R

Question 3

What pigment causes red hair?

Answer 3

Phaeomelanin
Eumelanin causes every other hair colour
MC1R turns phaemelanin into eumelanin

Question 4

What is a freckle (ephilides)

Answer 4

Clumpy distribution of melanocytes

One defective copy of MC1R

Question 5

What is an actinic letinges?

Answer 5

Age or liver spots related to chronic UV exposure

Found on face, forearms and dorsal arms

Question 6

Histologically what do actinic letinges look like?

Answer 6

Epidermis elongated rete ridges

Increase melanin and basal melanocytes

Question 7

What is a melanocytes naevus?

Answer 7

Benign melanocytic tumour that contains nevus cells

Question 8

How do naevus develop?

Answer 8

Junctional naevus in childhood - melanocytes proliferate to clusters of cells at the DEJ
Compound naevus in adolescence - junctional cluster and groups of cells in dermis
Intradermal naevus in adulthood - all junctional activity has ceased, entirely dermal

Question 9

What does a dysplastic naevus look like?

Answer 9

Generally over 6mm in diameter
Variegated pigment
Border asymmetry

Question 10

What is a sporadic dysplatic naevus?

Answer 10

Not inherited
One to several atypical naevus
Risk of MM slightly raised

Question 11

What is a familial dysplastic naevus?

Answer 11

Strong FH of melanoma
Autosomal inheritance with high penetrance
Lots and lots of atypical naevi
Lifetime risk of melanoma is 100%

Question 12

What do dysplastic naevi look like histologically?

Answer 12

Architectural atypia and cellular atypia
Host reactoin-fibrosis and inflammation
Epidermis not effaced

Question 13

What is a halo naevi?

Answer 13

Peripheral halo of depigmentation around naevus dude to lymphocytes attacking melanocytes in naevus causing regression

Question 14

What are blue naevi?

Answer 14

Entirely dermal and consist of pigment rich dendritic spindle cells
Cellular variant may have mitosis and mimic melanoma

Question 15

What is a spitz naevus?

Answer 15

Benign juvenile melanoma
Consist of large spindle elitheliod cells
Mimics melanoma

Question 16

What is the epidemiology of MM?

Answer 16

Commoner in females
Rare in childhood
Incidence peaks at middle age

Question 17

What is the aetiology of MM?

Answer 17

Sun exposure in childhood
Multifactorial
Most common on sun exposed sites - scalp, face, neck, arm, trunk, leg

Question 18

When should melanoma be suspected?

Answer 18

Change in shape
New pigmented lesions in adulthood
Irregular pigmentation 
Bleeding
Development of satellite nodules
Ulceration

Question 19

What are the different types of melanoma?

Answer 19

Superficial spreading - trunk and limbs
Acral/ mucosal
Lentigo maligna - sun damaged face/neck/scalp
Modular - trunk

Question 20

What are the different growth phases of MM?

Answer 20

Grow as macules when either entirely in situ or with dermal microinvasion - RGP
Melanoma cells will invade the dermis an expansile mass with mitosis - vertical growth phase

Question 21

What is the growth of nodular MM?

Answer 21

No clinical or microscopic evidence of RGP
Simply a nodule of VGP tumour
Very aggressive

Question 22

What is breslow thickness?

Answer 22

Deepest tumour from granular layer in millimetres

Question 23

What are the different breslow depths and survival rates at 5 years?

Answer 23

pTis - 100% survival
pT1 - < 1mm 90% survival 
pT2 - 1-2mm 80% survival 
pT3 - 2-4mm 55% survival
pT4 - >4mm 20% survival

Question 24

What are the breslow terms for ulceration?

Answer 24

Suffix b indicates tumour ulceration - pT3b

Question 25

What is satellite spread of MM?

Answer 25

Local dermal lymphatics

Question 26

Where are malignant melanomas likely to spread?

Answer 26

GI tract
Brain
Lungs

Question 27

How is melanoma treated?

Answer 27

Primary excision to give clear margins
Sentinel node biopsy - if positive perform regional lymphadenectomy
Chemo, immunotherapy, genetic therapies

Question 28

What mutations do acral melanomas tend to have and how can they be treated?

Answer 28

C-kit treated with imatinib

Question 29

What mutations do melanomas arising from intermittently sun exposed skin tend to have?

Answer 29

BRAF