Pathology Of Pigmented Skin Lesions Flashcards
Where do melanocytes migrate from the neural crest to?
Skin
Uveal tract
Lepitomeninges
What gene determines the balance of pigment in skin and hair?
MC1R
What pigment causes red hair?
Phaeomelanin
Eumelanin causes every other hair colour
MC1R turns phaemelanin into eumelanin
What is a freckle (ephilides)
Clumpy distribution of melanocytes
One defective copy of MC1R
What is an actinic letinges?
Age or liver spots related to chronic UV exposure
Found on face, forearms and dorsal arms
Histologically what do actinic letinges look like?
Epidermis elongated rete ridges
Increase melanin and basal melanocytes
What is a melanocytes naevus?
Benign melanocytic tumour that contains nevus cells
How do naevus develop?
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
What does a dysplastic naevus look like?
Generally over 6mm in diameter
Variegated pigment
Border asymmetry
What is a sporadic dysplatic naevus?
Not inherited
One to several atypical naevus
Risk of MM slightly raised
What is a familial dysplastic naevus?
Strong FH of melanoma
Autosomal inheritance with high penetrance
Lots and lots of atypical naevi
Lifetime risk of melanoma is 100%
What do dysplastic naevi look like histologically?
Architectural atypia and cellular atypia
Host reactoin-fibrosis and inflammation
Epidermis not effaced
What is a halo naevi?
Peripheral halo of depigmentation around naevus dude to lymphocytes attacking melanocytes in naevus causing regression
What are blue naevi?
Entirely dermal and consist of pigment rich dendritic spindle cells
Cellular variant may have mitosis and mimic melanoma
What is a spitz naevus?
Benign juvenile melanoma
Consist of large spindle elitheliod cells
Mimics melanoma
What is the epidemiology of MM?
Commoner in females
Rare in childhood
Incidence peaks at middle age
What is the aetiology of MM?
Sun exposure in childhood
Multifactorial
Most common on sun exposed sites - scalp, face, neck, arm, trunk, leg
When should melanoma be suspected?
Change in shape New pigmented lesions in adulthood Irregular pigmentation Bleeding Development of satellite nodules Ulceration
What are the different types of melanoma?
Superficial spreading - trunk and limbs
Acral/ mucosal
Lentigo maligna - sun damaged face/neck/scalp
Modular - trunk
What are the different growth phases of MM?
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
What is the growth of nodular MM?
No clinical or microscopic evidence of RGP
Simply a nodule of VGP tumour
Very aggressive
What is breslow thickness?
Deepest tumour from granular layer in millimetres
What are the different breslow depths and survival rates at 5 years?
pTis - 100% survival pT1 - < 1mm 90% survival pT2 - 1-2mm 80% survival pT3 - 2-4mm 55% survival pT4 - >4mm 20% survival
What are the breslow terms for ulceration?
Suffix b indicates tumour ulceration - pT3b
What is satellite spread of MM?
Local dermal lymphatics
Where are malignant melanomas likely to spread?
GI tract
Brain
Lungs
How is melanoma treated?
Primary excision to give clear margins
Sentinel node biopsy - if positive perform regional lymphadenectomy
Chemo, immunotherapy, genetic therapies
What mutations do acral melanomas tend to have and how can they be treated?
C-kit treated with imatinib
What mutations do melanomas arising from intermittently sun exposed skin tend to have?
BRAF
